<?xml version="1.0" encoding="US-ASCII"?>
<!-- DFIN New ActiveDisclosure (SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date :2024-05-01T15:05:51.3451+00:00 -->
<!-- Copyright (c) 2024 Donnelly Financial Solutions, Inc. All Rights Reserved. -->
<xsd:schema targetNamespace="http://sixthstreetspecialtylending.com/20240331" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:country="http://xbrl.sec.gov/country/2023" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2022-03-31" xmlns:cef="http://xbrl.sec.gov/cef/2023" xmlns:ecd-sub="http://xbrl.sec.gov/ecd-sub/2023" xmlns:ecd="http://xbrl.sec.gov/ecd/2023" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:dei="http://xbrl.sec.gov/dei/2023" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:cef-pre="http://xbrl.sec.gov/cef-pre/2023" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:srt="http://fasb.org/srt/2023" xmlns:us-gaap="http://fasb.org/us-gaap/2023" xmlns:tslx="http://sixthstreetspecialtylending.com/20240331" xmlns:xlink="http://www.w3.org/1999/xlink">
  <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/instance"/>
  <xsd:import schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" namespace="http://www.xbrl.org/2003/linkbase"/>
  <xsd:import schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" namespace="http://xbrl.org/2005/xbrldt"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/dei/2023/dei-2023.xsd" namespace="http://xbrl.sec.gov/dei/2023"/>
  <xsd:import schemaLocation="https://www.xbrl.org/2020/extensible-enumerations-2.0.xsd" namespace="http://xbrl.org/2020/extensible-enumerations-2.0"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/cef/2023/cef-2023.xsd" namespace="http://xbrl.sec.gov/cef/2023"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/ecd/2023/ecd-sub-2023.xsd" namespace="http://xbrl.sec.gov/ecd-sub/2023"/>
  <xsd:import schemaLocation="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd" namespace="http://fasb.org/us-gaap/2023"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/country/2023/country-2023.xsd" namespace="http://xbrl.sec.gov/country/2023"/>
  <xsd:import schemaLocation="https://www.xbrl.org/dtr/type/2022-03-31/types.xsd" namespace="http://www.xbrl.org/dtr/type/2022-03-31"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/cef/2023/cef-2023_pre.xsd" namespace="http://xbrl.sec.gov/cef-pre/2023"/>
  <xsd:import schemaLocation="https://xbrl.sec.gov/ecd/2023/ecd-2023.xsd" namespace="http://xbrl.sec.gov/ecd/2023"/>
  <xsd:import schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd" namespace="http://fasb.org/srt/2023"/>
  <xsd:annotation>
    <xsd:appinfo>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DocumentDocumentAndEntityInformation" id="Role_DocumentDocumentAndEntityInformation">
        <link:definition>100000 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnaudited" id="Role_StatementConsolidatedBalanceSheetsUnaudited">
        <link:definition>100010 - Statement - Consolidated Balance Sheets (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical" id="Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical">
        <link:definition>100020 - Statement - Consolidated Balance Sheets (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfOperationsUnaudited" id="Role_StatementConsolidatedStatementsOfOperationsUnaudited">
        <link:definition>100030 - Statement - Consolidated Statements of Operations (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnaudited" id="Role_StatementConsolidatedScheduleOfInvestmentsUnaudited">
        <link:definition>100040 - Statement - Consolidated Schedule of Investments (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical" id="Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical">
        <link:definition>100050 - Statement - Consolidated Schedule of Investments (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParentheticalDefault" id="Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParentheticalDefault">
        <link:definition>100050 - Statement - Consolidated Schedule of Investments (Unaudited) (Parenthetical) [Default]</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnaudited" id="StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnaudited">
        <link:definition>100060 - Statement - Consolidated Schedule of Investments (Affiliated Investments) (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParenthetical" id="StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParenthetical">
        <link:definition>100070 - Statement - Consolidated Schedule of Investments (Affiliated Investments) (Unaudited) (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParentheticalDefault" id="StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParentheticalDefault">
        <link:definition>100070 - Statement - Consolidated Schedule of Investments (Affiliated Investments) (Unaudited) (Parenthetical) [Default]</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited" id="Role_StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited">
        <link:definition>100080 - Statement - Consolidated Statements of Changes in Net Assets (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited" id="StatementConsolidatedStatementsOfCashFlowsUnaudited">
        <link:definition>100090 - Statement - Consolidated Statements of Cash Flows (Unaudited)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureOrganizationAndBasisOfPresentation" id="Role_DisclosureOrganizationAndBasisOfPresentation">
        <link:definition>995455 - Disclosure - Organization and Basis of Presentation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPolicies" id="Role_DisclosureSignificantAccountingPolicies">
        <link:definition>995465 - Disclosure - Significant Accounting Policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactions" id="Role_DisclosureAgreementsAndRelatedPartyTransactions">
        <link:definition>995475 - Disclosure - Agreements and Related Party Transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValue" id="Role_DisclosureInvestmentsAtFairValue">
        <link:definition>995485 - Disclosure - Investments at Fair Value</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivatives" id="Role_DisclosureDerivatives">
        <link:definition>995495 - Disclosure - Derivatives</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments" id="Role_DisclosureFairValueOfFinancialInstruments">
        <link:definition>995505 - Disclosure - Fair Value of Financial Instruments</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebt" id="Role_DisclosureDebt">
        <link:definition>995515 - Disclosure - Debt</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingencies" id="Role_DisclosureCommitmentsAndContingencies">
        <link:definition>995525 - Disclosure - Commitments and Contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssets" id="Role_DisclosureNetAssets">
        <link:definition>995535 - Disclosure - Net Assets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShare" id="DisclosureEarningsPerShare">
        <link:definition>995545 - Disclosure - Earnings per Share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividends" id="Role_DisclosureDividends">
        <link:definition>995555 - Disclosure - Dividends</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxes" id="DisclosureIncomeTaxes">
        <link:definition>995565 - Disclosure - Income Taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFinancialHighlights" id="Role_DisclosureFinancialHighlights">
        <link:definition>995575 - Disclosure - Financial Highlights</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSubsequentEvents" id="Role_DisclosureSubsequentEvents">
        <link:definition>995585 - Disclosure - Subsequent Events</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesPolicies" id="Role_DisclosureSignificantAccountingPoliciesPolicies">
        <link:definition>995595 - Disclosure - Significant Accounting Policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueTables" id="Role_DisclosureInvestmentsAtFairValueTables">
        <link:definition>995605 - Disclosure - Investments at Fair Value (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesTables" id="Role_DisclosureDerivativesTables">
        <link:definition>995615 - Disclosure - Derivatives (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsTables" id="Role_DisclosureFairValueOfFinancialInstrumentsTables">
        <link:definition>995625 - Disclosure - Fair Value of Financial Instruments (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtTables" id="Role_DisclosureDebtTables">
        <link:definition>995635 - Disclosure - Debt (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesTables" id="Role_DisclosureCommitmentsAndContingenciesTables">
        <link:definition>995645 - Disclosure - Commitments and Contingencies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsTables" id="Role_DisclosureNetAssetsTables">
        <link:definition>995655 - Disclosure - Net Assets (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareTables" id="DisclosureEarningsPerShareTables">
        <link:definition>995665 - Disclosure - Earnings Per Share (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsTables" id="Role_DisclosureDividendsTables">
        <link:definition>995675 - Disclosure - Dividends (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesTables" id="DisclosureIncomeTaxesTables">
        <link:definition>995685 - Disclosure - Income Taxes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFinancialHighlightsTables" id="Role_DisclosureFinancialHighlightsTables">
        <link:definition>995695 - Disclosure - Financial Highlights (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetails" id="Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetails">
        <link:definition>995705 - Disclosure - Significant Accounting Policies - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails" id="Role_DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails">
        <link:definition>995715 - Disclosure - Agreements and Related Party Transactions - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfInvestmentsAtFairValueDetails" id="Role_DisclosureInvestmentsAtFairValueSummaryOfInvestmentsAtFairValueDetails">
        <link:definition>995725 - Disclosure - Investments at Fair Value - Summary of Investments at Fair Value (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfIndustryCompositionOfInvestmentsAtFairValueDetails" id="Role_DisclosureInvestmentsAtFairValueSummaryOfIndustryCompositionOfInvestmentsAtFairValueDetails">
        <link:definition>995735 - Disclosure - Investments at Fair Value - Summary of Industry Composition of Investments at Fair Value (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueDetails" id="Role_DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueDetails">
        <link:definition>995745 - Disclosure - Investments at Fair Value - Summary of Geographic Composition of Investments at Fair Value (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueParentheticalDetails" id="DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueParentheticalDetails">
        <link:definition>995755 - Disclosure - Investments at Fair Value - Summary of Geographic Composition of Investments at Fair Value (Parenthetical) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails" id="Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails">
        <link:definition>995765 - Disclosure - Derivatives - Summary of Amounts Paid and Received on Interest Rate Swap Transactions, Excluding Upfront Fees (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesAdditionalInformationDetails" id="Role_DisclosureDerivativesAdditionalInformationDetails">
        <link:definition>995775 - Disclosure - Derivatives - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails" id="Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails">
        <link:definition>995785 - Disclosure - Fair Value of Financial Instruments - Fair Value Measurements of Investments (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsChangesInFairValueOfInvestmentsUsingLevel3InputsDetails" id="DisclosureFairValueOfFinancialInstrumentsChangesInFairValueOfInvestmentsUsingLevel3InputsDetails">
        <link:definition>995795 - Disclosure - Fair Value of Financial Instruments - Changes in Fair Value of Investments Using Level 3 Inputs (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsNetChangeInUnrealizedGainsOrLossesOnInvestmentsForWhichLevel3InputsWereUsedInDeterminingFairValueDetails" id="Role_DisclosureFairValueOfFinancialInstrumentsNetChangeInUnrealizedGainsOrLossesOnInvestmentsForWhichLevel3InputsWereUsedInDeterminingFairValueDetails">
        <link:definition>995805 - Disclosure - Fair Value of Financial Instruments - Net Change in Unrealized Gains or Losses on Investments for Which Level 3 Inputs were Used in Determining Fair Value (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsDetails" id="DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsDetails">
        <link:definition>995815 - Disclosure - Fair Value of Financial Instruments - Fair Value of Level 3 Investments at Fair Value and Significant Unobservable Inputs Used in Valuations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsParenthe" id="DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsParenthe">
        <link:definition>995825 - Disclosure - Fair Value of Financial Instruments - Fair Value of Level 3 Investments at Fair Value and Significant Unobservable Inputs Used in Valuations (Parenthetical) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfNotesDetails" id="DisclosureFairValueOfFinancialInstrumentsFairValueOfNotesDetails">
        <link:definition>995835 - Disclosure - Fair Value of Financial Instruments - Fair Value of Notes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtAdditionalInformationDetails" id="Role_DisclosureDebtAdditionalInformationDetails">
        <link:definition>995845 - Disclosure - Debt - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails" id="Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails">
        <link:definition>995855 - Disclosure - Debt - Schedule of Components of Interest Expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails" id="DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails">
        <link:definition>995865 - Disclosure - Debt - Schedule of Component of Carrying Value of Convertible Notes and Interest Rates (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfDebtObligationsDetails" id="Role_DisclosureDebtScheduleOfDebtObligationsDetails">
        <link:definition>995875 - Disclosure - Debt - Schedule of Debt Obligations (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfDebtObligationsParentheticalDetails" id="DisclosureDebtScheduleOfDebtObligationsParentheticalDetails">
        <link:definition>995885 - Disclosure - Debt - Schedule of Debt Obligations (Parenthetical) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesDetails" id="Role_DisclosureCommitmentsAndContingenciesScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesDetails">
        <link:definition>995895 - Disclosure - Commitments and Contingencies - Schedule of Commitments To Fund Investments In Current Portfolio Companies (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails" id="Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails">
        <link:definition>995905 - Disclosure - Commitments and Contingencies - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsAdditionalInformationDetails" id="Role_DisclosureNetAssetsAdditionalInformationDetails">
        <link:definition>995915 - Disclosure - Net Assets - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsScheduleOfSharesIssuedToStockholdersDetails" id="Role_DisclosureNetAssetsScheduleOfSharesIssuedToStockholdersDetails">
        <link:definition>995925 - Disclosure - Net Assets - Schedule of Shares Issued to Stockholders (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerCommonShareDetails" id="DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerCommonShareDetails">
        <link:definition>995935 - Disclosure - Earnings Per Share - Computation of Basic and Diluted Earnings Per Common Share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsSummaryOfDividendsDeclaredDetails" id="Role_DisclosureDividendsSummaryOfDividendsDeclaredDetails">
        <link:definition>995945 - Disclosure - Dividends - Summary of Dividends Declared (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsDetails" id="DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsDetails">
        <link:definition>995955 - Disclosure - Income Taxes - Summary Of Tax Character Of Shareholder Distributions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsParentheticalDetails" id="DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsParentheticalDetails">
        <link:definition>995965 - Disclosure - Income Taxes - Summary Of Tax Character Of Shareholder Distributions (Parenthetical) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxBasisComponentsOfDistributableEarningsDetails" id="DisclosureIncomeTaxesSummaryOfTaxBasisComponentsOfDistributableEarningsDetails">
        <link:definition>995975 - Disclosure - Income Taxes - Summary of Tax Basis Components of Distributable Earnings (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfReconciliationIncreaseInNetAssetsDetails" id="DisclosureIncomeTaxesSummaryOfReconciliationIncreaseInNetAssetsDetails">
        <link:definition>995985 - Disclosure - Income Taxes - Summary of Reconciliation Increase in Net Assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetails" id="DisclosureIncomeTaxesAdditionalInformationDetails">
        <link:definition>995995 - Disclosure - Income Taxes - Additional Information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingDetails" id="DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingDetails">
        <link:definition>996005 - Disclosure - Financial Highlights - Summary of Financial Highlights for One Share Common Stock Outstanding (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingParentheticalDetails" id="DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingParentheticalDetails">
        <link:definition>996015 - Disclosure - Financial Highlights - Summary of Financial Highlights for One Share Common Stock Outstanding (Parenthetical) (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbase id="lnk">
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple"/>
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple"/>
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple"/>
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple"/>
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DocumentDocumentAndEntityInformation" xlink:href="tslx-20240331.xsd#Role_DocumentDocumentAndEntityInformation" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnaudited" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedBalanceSheetsUnaudited" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfOperationsUnaudited" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedStatementsOfOperationsUnaudited" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnaudited" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedScheduleOfInvestmentsUnaudited" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnaudited" xlink:href="tslx-20240331.xsd#StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnaudited" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParenthetical" xlink:href="tslx-20240331.xsd#StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParenthetical" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited" xlink:href="tslx-20240331.xsd#StatementConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="simple"/>
        <link:roleRef roleURI="http://xbrl.sec.gov/cef/role/N2" xlink:href="https://xbrl.sec.gov/cef/2023/cef-2023.xsd#N2" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureOrganizationAndBasisOfPresentation" xlink:href="tslx-20240331.xsd#Role_DisclosureOrganizationAndBasisOfPresentation" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPolicies" xlink:href="tslx-20240331.xsd#Role_DisclosureSignificantAccountingPolicies" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactions" xlink:href="tslx-20240331.xsd#Role_DisclosureAgreementsAndRelatedPartyTransactions" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValue" xlink:href="tslx-20240331.xsd#Role_DisclosureInvestmentsAtFairValue" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivatives" xlink:href="tslx-20240331.xsd#Role_DisclosureDerivatives" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments" xlink:href="tslx-20240331.xsd#Role_DisclosureFairValueOfFinancialInstruments" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebt" xlink:href="tslx-20240331.xsd#Role_DisclosureDebt" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingencies" xlink:href="tslx-20240331.xsd#Role_DisclosureCommitmentsAndContingencies" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssets" xlink:href="tslx-20240331.xsd#Role_DisclosureNetAssets" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShare" xlink:href="tslx-20240331.xsd#DisclosureEarningsPerShare" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividends" xlink:href="tslx-20240331.xsd#Role_DisclosureDividends" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxes" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxes" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFinancialHighlights" xlink:href="tslx-20240331.xsd#Role_DisclosureFinancialHighlights" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSubsequentEvents" xlink:href="tslx-20240331.xsd#Role_DisclosureSubsequentEvents" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesPolicies" xlink:href="tslx-20240331.xsd#Role_DisclosureSignificantAccountingPoliciesPolicies" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueTables" xlink:href="tslx-20240331.xsd#Role_DisclosureInvestmentsAtFairValueTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesTables" xlink:href="tslx-20240331.xsd#Role_DisclosureDerivativesTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsTables" xlink:href="tslx-20240331.xsd#Role_DisclosureFairValueOfFinancialInstrumentsTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtTables" xlink:href="tslx-20240331.xsd#Role_DisclosureDebtTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesTables" xlink:href="tslx-20240331.xsd#Role_DisclosureCommitmentsAndContingenciesTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsTables" xlink:href="tslx-20240331.xsd#Role_DisclosureNetAssetsTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareTables" xlink:href="tslx-20240331.xsd#DisclosureEarningsPerShareTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsTables" xlink:href="tslx-20240331.xsd#Role_DisclosureDividendsTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesTables" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxesTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFinancialHighlightsTables" xlink:href="tslx-20240331.xsd#Role_DisclosureFinancialHighlightsTables" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfInvestmentsAtFairValueDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureInvestmentsAtFairValueSummaryOfInvestmentsAtFairValueDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfIndustryCompositionOfInvestmentsAtFairValueDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureInvestmentsAtFairValueSummaryOfIndustryCompositionOfInvestmentsAtFairValueDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueParentheticalDetails" xlink:href="tslx-20240331.xsd#DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueParentheticalDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureDerivativesAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsChangesInFairValueOfInvestmentsUsingLevel3InputsDetails" xlink:href="tslx-20240331.xsd#DisclosureFairValueOfFinancialInstrumentsChangesInFairValueOfInvestmentsUsingLevel3InputsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsNetChangeInUnrealizedGainsOrLossesOnInvestmentsForWhichLevel3InputsWereUsedInDeterminingFairValueDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureFairValueOfFinancialInstrumentsNetChangeInUnrealizedGainsOrLossesOnInvestmentsForWhichLevel3InputsWereUsedInDeterminingFairValueDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsDetails" xlink:href="tslx-20240331.xsd#DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsParenthe" xlink:href="tslx-20240331.xsd#DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsParenthe" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfNotesDetails" xlink:href="tslx-20240331.xsd#DisclosureFairValueOfFinancialInstrumentsFairValueOfNotesDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureDebtAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails" xlink:href="tslx-20240331.xsd#DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfDebtObligationsDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureDebtScheduleOfDebtObligationsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfDebtObligationsParentheticalDetails" xlink:href="tslx-20240331.xsd#DisclosureDebtScheduleOfDebtObligationsParentheticalDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureCommitmentsAndContingenciesScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureNetAssetsAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsScheduleOfSharesIssuedToStockholdersDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureNetAssetsScheduleOfSharesIssuedToStockholdersDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerCommonShareDetails" xlink:href="tslx-20240331.xsd#DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerCommonShareDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsSummaryOfDividendsDeclaredDetails" xlink:href="tslx-20240331.xsd#Role_DisclosureDividendsSummaryOfDividendsDeclaredDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsDetails" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsParentheticalDetails" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsParentheticalDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxBasisComponentsOfDistributableEarningsDetails" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxesSummaryOfTaxBasisComponentsOfDistributableEarningsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfReconciliationIncreaseInNetAssetsDetails" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxesSummaryOfReconciliationIncreaseInNetAssetsDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetails" xlink:href="tslx-20240331.xsd#DisclosureIncomeTaxesAdditionalInformationDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingDetails" xlink:href="tslx-20240331.xsd#DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingParentheticalDetails" xlink:href="tslx-20240331.xsd#DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingParentheticalDetails" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParentheticalDefault" xlink:href="tslx-20240331.xsd#Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParentheticalDefault" xlink:type="simple"/>
        <link:roleRef roleURI="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParentheticalDefault" xlink:href="tslx-20240331.xsd#StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParentheticalDefault" xlink:type="simple"/>
        <link:roleRef roleURI="http://xbrl.sec.gov/cef/role/RiskOnly" xlink:href="https://xbrl.sec.gov/cef/2023/cef-2023.xsd#RiskOnly" xlink:type="simple"/>
        <link:roleRef roleURI="http://xbrl.sec.gov/cef/role/SecurityOnly" xlink:href="https://xbrl.sec.gov/cef/2023/cef-2023.xsd#SecurityOnly" xlink:type="simple"/>
        <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-roles-2023.xsd#eedm" xlink:type="simple"/>
        <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedLabel" xlink:type="simple"/>
        <link:roleRef roleURI="http://www.xbrl.org/2009/role/negatedTotalLabel" xlink:href="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd#negatedTotalLabel" xlink:type="simple"/>
        <link:labelLink xlink:role="http://www.xbrl.org/2003/role/link" xlink:title="labelLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentTransitionReport" xlink:label="dei_DocumentTransitionReport"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapFourMember" xlink:label="tslx_InterestRateSwapFourMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" xlink:label="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" xlink:label="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableAmountPerShare" xlink:label="us-gaap_DividendsPayableAmountPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HumanResourceSupportServicesMember" xlink:label="tslx_HumanResourceSupportServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" xlink:label="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IbisIntermediateCoMember" xlink:label="tslx_IbisIntermediateCoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnInvestments" xlink:label="us-gaap_UnrealizedGainLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtCost" xlink:label="us-gaap_InvestmentOwnedAtCost"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="us-gaap_FairValueInputsLevel1Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation" xlink:label="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_WeightedAverageMember" xlink:label="srt_WeightedAverageMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresTextBlock" xlink:label="us-gaap_FairValueDisclosuresTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromShortTermDebt" xlink:label="us-gaap_ProceedsFromShortTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BearOpCoLLCMember" xlink:label="tslx_BearOpCoLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TotalReturnBasedOnMarketValue" xlink:label="tslx_TotalReturnBasedOnMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_SE" xlink:label="country_SE"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredDuringThePeriod" xlink:label="tslx_DividendsDeclaredDuringThePeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverMember" xlink:label="tslx_RevolverMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentInterestRatePaidInKind" xlink:label="us-gaap_InvestmentInterestRatePaidInKind"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RatioOfIndebtednessToNetCapital1" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventsTextBlock" xlink:label="us-gaap_SubsequentEventsTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncome" xlink:label="us-gaap_OtherNonoperatingIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BanyanSoftwareHoldingsLlcMember" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_NL" xlink:label="country_NL"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OriginalIssueDiscountNetOfAccretion" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="us-gaap_ScheduleOfStockByClassTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="us-gaap_InvestmentsFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems" xlink:label="us-gaap_ClassOfStockLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsAbstract" xlink:label="us-gaap_RelatedPartyTransactionsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" xlink:label="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince" xlink:label="dei_EntityAddressStateOrProvince"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AzuriteIntermediateHoldingsIncMember" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BaseDividendMember" xlink:label="tslx_BaseDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ForeScoutTechnologiesIncMember" xlink:label="tslx_ForeScoutTechnologiesIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAxis" xlink:label="us-gaap_DividendsAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementAndIncentiveFeeWaived" xlink:label="tslx_ManagementAndIncentiveFeeWaived"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LucidworksIncMember" xlink:label="tslx_LucidworksIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UndistributedNetRealizedGainsTaxBasis" xlink:label="tslx_UndistributedNetRealizedGainsTaxBasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" xlink:label="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown" xlink:label="dei_EntityAddressCityOrTown"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="us-gaap_RelatedPartyTransactionLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestmentsMember" xlink:label="tslx_StructuredCreditInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureTextBlock" xlink:label="us-gaap_DebtDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AssetValuationWaterfallMember" xlink:label="tslx_AssetValuationWaterfallMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverEquityMember" xlink:label="tslx_RevolverEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HornetsecurityHoldingGmbhMember" xlink:label="tslx_HornetsecurityHoldingGmbhMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialServicesSectorMember" xlink:label="us-gaap_FinancialServicesSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInAdditionalPaidInCapital" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfStockholdersEquityAbstract" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawMember" xlink:label="tslx_DelayedDrawMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="us-gaap_DebtInstrumentMaturityDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityOfferingExpensesPolicyTextBlock" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherPayablesToAffiliate" xlink:label="tslx_OtherPayablesToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeePayable" xlink:label="us-gaap_ManagementFeePayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeInterest" xlink:label="us-gaap_InvestmentIncomeInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="srt_ScenarioUnspecifiedDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonShares" xlink:label="us-gaap_TreasuryStockCommonShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_CA" xlink:label="country_CA"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember" xlink:label="us-gaap_RelatedPartyMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber" xlink:label="dei_EntityTaxIdentificationNumber"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NortheastMember" xlink:label="tslx_NortheastMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DiscoParentIncMember" xlink:label="tslx_DiscoParentIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BusinessServicesMember" xlink:label="tslx_BusinessServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AutomotiveMember" xlink:label="tslx_AutomotiveMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" xlink:label="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyEightNotesMember" xlink:label="tslx_TwentyTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RisksAssociatedWithChangesInInterestRatesMember" xlink:label="tslx_RisksAssociatedWithChangesInInterestRatesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TruckLiteCoLlcMember" xlink:label="tslx_TruckLiteCoLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionOriginalDebtAmount1" xlink:label="us-gaap_DebtConversionOriginalDebtAmount1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InsuranceMember" xlink:label="tslx_InsuranceMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US" xlink:label="country_US"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet" xlink:label="us-gaap_InvestmentIncomeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HealthcareSectorMember" xlink:label="us-gaap_HealthcareSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SignificantAccountingPoliciesTextBlock" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AlphaMidcoIncMember" xlink:label="tslx_AlphaMidcoIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_AU" xlink:label="country_AU"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioForecastMember" xlink:label="srt_ScenarioForecastMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HotelGamingAndLeisureMember" xlink:label="tslx_HotelGamingAndLeisureMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeForwardMember" xlink:label="us-gaap_ForeignExchangeForwardMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapOneMember" xlink:label="tslx_InterestRateSwapOneMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentBasisSpreadVariableRate" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdjustmentsAbstract" xlink:label="tslx_AdjustmentsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BlueSnapIncMember" xlink:label="tslx_BlueSnapIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtPolicyTextBlock" xlink:label="us-gaap_DebtPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestAndDebtExpense" xlink:label="us-gaap_InterestAndDebtExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapThreeMember" xlink:label="tslx_InterestRateSwapThreeMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TangoManagementConsultingLLCMember" xlink:label="tslx_TangoManagementConsultingLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1" xlink:label="us-gaap_DebtConversionConvertedInstrumentAmount1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwaps" xlink:label="tslx_InterestRateSwaps"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BaseRateMember" xlink:label="us-gaap_BaseRateMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxReclassificationOfStockholdersEquity" xlink:label="tslx_TaxReclassificationOfStockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DebtConversionPrincipalAmount" xlink:label="tslx_DebtConversionPrincipalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawRevolverPreferredEquityMember" xlink:label="tslx_DelayedDrawRevolverPreferredEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SouthMember" xlink:label="tslx_SouthMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNonQualifyingAssets" xlink:label="tslx_PercentageOfNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash" xlink:label="us-gaap_Cash"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RetailAndConsumerProductsMember" xlink:label="tslx_RetailAndConsumerProductsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TRPAssetsLLCMember" xlink:label="tslx_TRPAssetsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGains" xlink:label="tslx_IncentiveFeesOnNetCapitalGains"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesPaid" xlink:label="us-gaap_IncomeTaxesPaid"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="us-gaap_ValuationTechniqueDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerSharePolicyTextBlock" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BabylonFincoLimitedMember" xlink:label="tslx_BabylonFincoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfShortTermDebt" xlink:label="us-gaap_RepaymentsOfShortTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DerivativeNotionalAmountHeldDuringPeriod" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OutsystemsLuxcoMember" xlink:label="tslx_OutsystemsLuxcoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherTemporaryDifferences" xlink:label="tslx_OtherTemporaryDifferences"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventsAbstract" xlink:label="us-gaap_SubsequentEventsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InternetServicesMember" xlink:label="tslx_InternetServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxableIncome" xlink:label="tslx_TaxableIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPaidNet" xlink:label="us-gaap_InterestPaidNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpenseDirectorsFees" xlink:label="us-gaap_NoninterestExpenseDirectorsFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestmentMeasurementInput" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapSixMember" xlink:label="tslx_InterestRateSwapSixMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAbstract" xlink:label="us-gaap_LiabilitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems" xlink:label="us-gaap_DerivativeLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestments" xlink:label="tslx_StructuredCreditInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnApril232027Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesRealizedAndPayableToAdvisor" xlink:label="tslx_IncentiveFeesRealizedAndPayableToAdvisor"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IRGSEHoldingCorpMember" xlink:label="tslx_IRGSEHoldingCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FullsteamOperationsLlcMember" xlink:label="tslx_FullsteamOperationsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="us-gaap_EarningsPerShareAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_LU" xlink:label="country_LU"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UndistributedNetInvestmentIncomeTaxBasis" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NumberOfInvestments" xlink:label="tslx_NumberOfInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramExpirationDate" xlink:label="us-gaap_StockRepurchaseProgramExpirationDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OrdinaryIncome" xlink:label="tslx_OrdinaryIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementScenarioAxis" xlink:label="srt_StatementScenarioAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetwrixCorpMember" xlink:label="tslx_NetwrixCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManufacturingMember" xlink:label="tslx_ManufacturingMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdviserMember" xlink:label="tslx_AdviserMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaidInKindInterestIncome" xlink:label="tslx_PaidInKindInterestIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Investments" xlink:label="us-gaap_Investments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ArtisanBidcoIncMember" xlink:label="tslx_ArtisanBidcoIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" xlink:label="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="us-gaap_MeasurementInputTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RisksAssociatedWithConflictsOfInterestMember" xlink:label="tslx_RisksAssociatedWithConflictsOfInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtWeightedAverageInterestRateOverTime" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsFairValueDisclosureNet" xlink:label="tslx_InvestmentsFairValueDisclosureNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver" xlink:label="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeDividend" xlink:label="us-gaap_InvestmentIncomeDividend"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BCTOAcePurchaserIncMember" xlink:label="tslx_BCTOAcePurchaserIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetUnrealizedGainsOnInvestments" xlink:label="tslx_NetUnrealizedGainsOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CurrentMarketPricePerSharePercentage" xlink:label="tslx_CurrentMarketPricePerSharePercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OilGasAndConsumableFuelsMember" xlink:label="tslx_OilGasAndConsumableFuelsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PdiTaHoldingsIncMember" xlink:label="tslx_PdiTaHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SignificantAccountingPoliciesTable" xlink:label="tslx_SignificantAccountingPoliciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="us-gaap_RelatedPartyTransactionDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpenseForFederalExciseTax" xlink:label="tslx_NetExpenseForFederalExciseTax"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsNet" xlink:label="us-gaap_AssetsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendDeclaredFromRealizedGainsPerShare" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramPeriodInForce1" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsOwnedEstimatedCostBasis" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode" xlink:label="dei_EntityAddressPostalZipCode"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" xlink:label="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInteractiveDataCurrent" xlink:label="dei_EntityInteractiveDataCurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyThreeNotesMember" xlink:label="tslx_TwentyTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputDiscountRateMember" xlink:label="us-gaap_MeasurementInputDiscountRateMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="us-gaap_OverAllotmentOptionMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract" xlink:label="us-gaap_EquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HeritageEnvironmentalServicesIncMember" xlink:label="tslx_HeritageEnvironmentalServicesIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_Project44IncMember" xlink:label="tslx_Project44IncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="dei_EntityIncorporationStateCountryCode"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="us-gaap_EarningsPerShareBasicAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PrimeRevenueIncMember" xlink:label="tslx_PrimeRevenueIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LineOfCreditFacilityStatedMaturityDate" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber" xlink:label="dei_LocalPhoneNumber"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AgreementTerminationPeriodWithoutPenalty" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_WestMember" xlink:label="tslx_WestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RapidDataGmbhUnternehmensberatungMember" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawRevolverEquityMember" xlink:label="tslx_DelayedDrawRevolverEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LineOfCreditFacilityExtendedDate" xlink:label="tslx_LineOfCreditFacilityExtendedDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BctoBluebillBuyerIncMember" xlink:label="tslx_BctoBluebillBuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AlaskaBidcoOyMember" xlink:label="tslx_AlaskaBidcoOyMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInDistributableEarnings" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpense" xlink:label="tslx_NetExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentAdvisoryAgreementMember" xlink:label="tslx_InvestmentAdvisoryAgreementMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AmericanAchievementCorpMember" xlink:label="tslx_AmericanAchievementCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTenMember" xlink:label="tslx_InterestRateSwapTenMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Dividends" xlink:label="us-gaap_Dividends"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SupplementalDividendMember" xlink:label="tslx_SupplementalDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList" xlink:label="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="us-gaap_RelatedPartyTransactionAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityAverageOutstandingAmount" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfDividends" xlink:label="us-gaap_PaymentsOfDividends"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AccountingStandardsUpdate202206Member" xlink:label="tslx_AccountingStandardsUpdate202206Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ElysianFincoLtdMember" xlink:label="tslx_ElysianFincoLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseMember" xlink:label="us-gaap_InterestExpenseMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateDerivativesAtFairValueNet" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherGeneralAndAdministrativeExpense" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsTextBlock" xlink:label="tslx_DividendsTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ChemicalsMember" xlink:label="tslx_ChemicalsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTwelveMember" xlink:label="tslx_InterestRateSwapTwelveMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode" xlink:label="dei_CityAreaCode"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapEightMember" xlink:label="tslx_InterestRateSwapEightMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember" xlink:label="us-gaap_LetterOfCreditMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AvalaraIncMember" xlink:label="tslx_AvalaraIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_KangarooBidcoASMember" xlink:label="tslx_KangarooBidcoASMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentPolicyTextBlock" xlink:label="us-gaap_InvestmentPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_GB" xlink:label="country_GB"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueNetAssetLiability" xlink:label="us-gaap_FairValueNetAssetLiability"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardLineItems" xlink:label="us-gaap_TaxCreditCarryforwardLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_GainLossFormAdjustmentOfPaidInKindInterest" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfAnEffectiveHedge" xlink:label="tslx_FairValueOfAnEffectiveHedge"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock" xlink:label="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfFinancingCosts" xlink:label="us-gaap_PaymentsOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NondeductibleFederalExciseTaxPercentage" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TransportationMember" xlink:label="tslx_TransportationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_FI" xlink:label="country_FI"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PurchasesAndOriginationsOfInvestmentsNet" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ValuationTechniqueCostOfInvestmentsMember" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverAndPartnershipInterestMember" xlink:label="tslx_RevolverAndPartnershipInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentDueDate" xlink:label="tslx_InvestmentDueDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ObligorGroupMember" xlink:label="srt_ObligorGroupMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="us-gaap_LettersOfCreditOutstandingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RepaymentsOnInvestments" xlink:label="tslx_RepaymentsOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiscalPeriod" xlink:label="us-gaap_FiscalPeriod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedLossOnInvestments" xlink:label="tslx_UnrealizedLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesPolicyTextBlock" xlink:label="us-gaap_DerivativesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementFeeWaiverHurdle" xlink:label="tslx_ManagementFeeWaiverHurdle"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLosses" xlink:label="us-gaap_RealizedInvestmentGainsLosses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_GalileoParentincMember" xlink:label="tslx_GalileoParentincMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LeverageWaiverMember" xlink:label="tslx_LeverageWaiverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PartnershipInterestOwnershipPercentage" xlink:label="tslx_PartnershipInterestOwnershipPercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradingSecuritiesDebt" xlink:label="us-gaap_TradingSecuritiesDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EdgeBidcoBVMember" xlink:label="tslx_EdgeBidcoBVMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfDebtTableTextBlock" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfessionalFees" xlink:label="us-gaap_ProfessionalFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDomain" xlink:label="us-gaap_DividendsDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SwapSettlement" xlink:label="tslx_SwapSettlement"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AsgIiLlcMember" xlink:label="tslx_AsgIiLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayableFairValueDisclosure" xlink:label="us-gaap_NotesPayableFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BtrsHoldingIncMember" xlink:label="tslx_BtrsHoldingIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxCostOfInvestments" xlink:label="tslx_TaxCostOfInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList" xlink:label="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ExtinguishmentOfDebtAmount" xlink:label="us-gaap_ExtinguishmentOfDebtAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HippoXpaBidcoAbMember" xlink:label="tslx_HippoXpaBidcoAbMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EMSLinqIncMember" xlink:label="tslx_EMSLinqIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncome" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName" xlink:label="dei_SecurityExchangeName"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DomesticCountryMember" xlink:label="us-gaap_DomesticCountryMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTwoMember" xlink:label="tslx_InterestRateSwapTwoMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DistributedEarnings" xlink:label="us-gaap_DistributedEarnings"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PerShareMarketValueAtEndPeriod" xlink:label="tslx_PerShareMarketValueAtEndPeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnApril242029Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsAtFairValueTextBlock" xlink:label="tslx_InvestmentsAtFairValueTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayable" xlink:label="us-gaap_NotesPayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesByIndustryAxis" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="us-gaap_TreasuryStockSharesAcquired"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PurchaseCommitmentToFundInvestment" xlink:label="tslx_PurchaseCommitmentToFundInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MarketApproachValuationTechniqueMember" xlink:label="us-gaap_MarketApproachValuationTechniqueMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherBookTaxDifferences" xlink:label="tslx_OtherBookTaxDifferences"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OfficeProductsMember" xlink:label="tslx_OfficeProductsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CommunicationsMember" xlink:label="tslx_CommunicationsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber" xlink:label="dei_EntityFileNumber"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ApteanIncMember" xlink:label="tslx_ApteanIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain" xlink:label="us-gaap_PledgedStatusDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredTaxAssetsGross" xlink:label="us-gaap_DeferredTaxAssetsGross"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities" xlink:label="us-gaap_OtherLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ExtraHopNetworksIncMember" xlink:label="tslx_ExtraHopNetworksIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdditionalAggregatePrincipalAmount" xlink:label="tslx_AdditionalAggregatePrincipalAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AxonifyIncMember" xlink:label="tslx_AxonifyIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_DE" xlink:label="country_DE"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PassportLabsIncMember" xlink:label="tslx_PassportLabsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsPolicyTextBlock" xlink:label="tslx_DividendsPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapSevenMember" xlink:label="tslx_InterestRateSwapSevenMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine2" xlink:label="dei_EntityAddressAddressLine2"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitySmallBusiness" xlink:label="dei_EntitySmallBusiness"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityShellCompany" xlink:label="dei_EntityShellCompany"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAbstract" xlink:label="us-gaap_DividendsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableLineItems" xlink:label="us-gaap_DividendsPayableLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfDerivatives" xlink:label="us-gaap_GainLossOnSaleOfDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAcquisitionDate" xlink:label="us-gaap_InvestmentAcquisitionDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareTextBlock" xlink:label="us-gaap_EarningsPerShareTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherIncomePolicyTextBlock" xlink:label="tslx_OtherIncomePolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1" xlink:label="dei_EntityAddressAddressLine1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestments" xlink:label="tslx_EquityAndOtherInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ErlingLuxBidcoSarlMember" xlink:label="tslx_ErlingLuxBidcoSarlMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeApproachValuationTechniqueMember" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IssuanceOfCommonStockNetOfOfferingCosts" xlink:label="tslx_IssuanceOfCommonStockNetOfOfferingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash" xlink:label="us-gaap_RestrictedCash"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BenNevisMidcoLimitedMember" xlink:label="tslx_BenNevisMidcoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BayshoreIntermediate2LPMember" xlink:label="tslx_BayshoreIntermediate2LPMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncentiveFeeExpense" xlink:label="us-gaap_IncentiveFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapElevenMember" xlink:label="tslx_InterestRateSwapElevenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CrewlineBuyerIncMember" xlink:label="tslx_CrewlineBuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDeclaredTableTextBlock" xlink:label="us-gaap_DividendsDeclaredTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfIncentiveFeeRate" xlink:label="tslx_PercentageOfIncentiveFeeRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableTable" xlink:label="us-gaap_DividendsPayableTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawEquityMember" xlink:label="tslx_DelayedDrawEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle" xlink:label="dei_Security12bTitle"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeeExpense" xlink:label="us-gaap_ManagementFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesIndustryMember" xlink:label="us-gaap_EquitySecuritiesIndustryMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DeferredOrganizationCosts" xlink:label="tslx_DeferredOrganizationCosts"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LegislationAllowsToIncurAdditionalLeverageMember" xlink:label="tslx_LegislationAllowsToIncurAdditionalLeverageMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ArrowbuyerIncMember" xlink:label="tslx_ArrowbuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonMember" xlink:label="us-gaap_TreasuryStockCommonMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember" xlink:label="us-gaap_InterestRateSwapMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherIncomeForTaxPurposesNotBook" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable" xlink:label="us-gaap_DerivativeTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit" xlink:label="us-gaap_LineOfCredit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherExpensesNotCurrentlyDeductible" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyNineNotesMember" xlink:label="tslx_TwentyTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesOffsettingFairValueAmountsPolicy" xlink:label="us-gaap_DerivativesOffsettingFairValueAmountsPolicy"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardTable" xlink:label="us-gaap_TaxCreditCarryforwardTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CordanceOperationsLlcMember" xlink:label="tslx_CordanceOperationsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainsLossesOnIncomeTaxProvision" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EducationMember" xlink:label="tslx_EducationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnfundedLoanCommitmentMember" xlink:label="us-gaap_UnfundedLoanCommitmentMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapFiveMember" xlink:label="tslx_InterestRateSwapFiveMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ReliaQuestHoldingsLLCMember" xlink:label="tslx_ReliaQuestHoldingsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MarcuraEquitiesLtdMember" xlink:label="tslx_MarcuraEquitiesLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AssetCoveragePercentage" xlink:label="tslx_AssetCoveragePercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LeantaasHoldingsIncMember" xlink:label="tslx_LeantaasHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_NO" xlink:label="country_NO"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MidwestMember" xlink:label="tslx_MidwestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends" xlink:label="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EDBParentLLCMember" xlink:label="tslx_EDBParentLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInInterestReceivablePaidInKind" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapNineMember" xlink:label="tslx_InterestRateSwapNineMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitment" xlink:label="us-gaap_OtherCommitment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TotalReturnBasedOnNetAssetValue" xlink:label="tslx_TotalReturnBasedOnNetAssetValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentInterestRate" xlink:label="us-gaap_InvestmentInterestRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentQuarterlyReport" xlink:label="dei_DocumentQuarterlyReport"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdministrationAgreementMember" xlink:label="tslx_AdministrationAgreementMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssets" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SkylarkUkDebtcoLimitedMember" xlink:label="tslx_SkylarkUkDebtcoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetAssetValuePerShare" xlink:label="us-gaap_NetAssetValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CostModelMember" xlink:label="tslx_CostModelMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BlackScholesModelMember" xlink:label="tslx_BlackScholesModelMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MarketingServicesMember" xlink:label="tslx_MarketingServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusAxis" xlink:label="us-gaap_PledgedStatusAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainOnInvestments" xlink:label="tslx_UnrealizedGainOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawAndRevolverMember" xlink:label="tslx_DelayedDrawAndRevolverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LongTermCapitalGains" xlink:label="tslx_LongTermCapitalGains"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EmploymentHeroHoldingsPtyLtdMember" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LaramieEnergyLLCMember" xlink:label="tslx_LaramieEnergyLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestReceivable" xlink:label="us-gaap_InterestReceivable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DyeDurhamCorpMember" xlink:label="tslx_DyeDurhamCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendPayableDateToBePaidDayMonthAndYear" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SlBuyerCorpMember" xlink:label="tslx_SlBuyerCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="srt_ConsolidatedEntitiesAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CoupaHoldingsLLCMember" xlink:label="tslx_CoupaHoldingsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ThreeMonthLiborMember" xlink:label="tslx_ThreeMonthLiborMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyRepurchaseOfDebtPerShare" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SignificantAccountingPoliciesLineItems" xlink:label="tslx_SignificantAccountingPoliciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_KyribaCorpMember" xlink:label="tslx_KyribaCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableNature" xlink:label="us-gaap_DividendsPayableNature"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfDerivativeInstrumentsTextBlock" xlink:label="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawAndMembershipInterestMember" xlink:label="tslx_DelayedDrawAndMembershipInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputComparabilityAdjustmentMember" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyFourNotesMember" xlink:label="tslx_TwentyTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_WranglerTopcoLlcMember" xlink:label="tslx_WranglerTopcoLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PingIdentityCorporationMember" xlink:label="tslx_PingIdentityCorporationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HirevueIncMember" xlink:label="tslx_HirevueIncMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UseOfEstimates" xlink:label="us-gaap_UseOfEstimates"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapThirteenMember" xlink:label="tslx_InterestRateSwapThirteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentySixNotesMember" xlink:label="tslx_TwentyTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureTextBlock" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueAxis" xlink:label="us-gaap_ValuationTechniqueAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ProceedsFromInvestmentsNet" xlink:label="tslx_ProceedsFromInvestmentsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromUnsecuredNotesPayable" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherMember" xlink:label="tslx_OtherMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestment" xlink:label="us-gaap_AlternativeInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralMember" xlink:label="us-gaap_AssetPledgedAsCollateralMember"/>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap four.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Net Asset from Operations Increase Decrease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company net asset from operations increase decrease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">DebtInstrumentDescriptionOfLondonInterbankOfferedRateLIBORVariableRateBasis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">DebtInstrumentDescriptionOfLondonInterbankOfferedRateLIBORVariableRateBasis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument description of london interbank offered rate LIBOR variable rate basis.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Hedge, Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Amount Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableAmountPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HumanResourceSupportServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Human Resource Support Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HumanResourceSupportServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Human Resource Support Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HumanResourceSupportServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Human Resource Support Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax refund from operating loss carryback to previous tax years</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Refund from Operating Loss Carryback to Previous Tax Years</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax refund from operating loss carryback to previous tax years.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Geographical</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisIntermediateCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ibis Intermediate Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisIntermediateCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ibis Intermediate Co [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IbisIntermediateCoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ibis Intermediate Co.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of all pre-incentive fee net investment income after catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of All Pre Incentive Fee Net Investment Income After Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of all pre-Incentive Fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net unrealized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net change in unrealized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss) on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net Change In Unrealized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Investments at amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment at amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes, 2026 Notes, 2028 Notes and 2029 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Twenty Six Twenty Eight And Twenty Nine Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four twenty six twenty eight and twenty nine notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense Ratio before Incentive Allocation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ratio of net expenses to average net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_WeightedAverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Discounted Cash Flow Model</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique, Discounted Cash Flow [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax liability pertaining to unrealized gains on investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Liability Pertaining to Unrealized Gains Related to Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred tax liability pertaining to unrealized gains related to investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Gain (Loss) Included in Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Short-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Short-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Borrowings on debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BearOpCoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bear OpCo, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BearOpCoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bear Op Co L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BearOpCoLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bear OpCo, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on market value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Return Based On Market Value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Return Based On Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_SE_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sweden</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_SE_lbl" xlink:role="http://www.xbrl.org/2003/role/label">SWEDEN</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Organization and Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends declared during the period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Declared During The Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredDuringThePeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate, PIK</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRatePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Interest Rate, Paid in Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ratio of Indebtedness to Net Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset coverage ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Events</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Banyan Software Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Banyan Software Holdings LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Banyan Software Holdings LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Record Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date of Record</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends record date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NL_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Netherlands</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NL_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NETHERLANDS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Measurements of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Original issue discount, net of accretion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Original issue discount, net of accretion.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Original Issue Discount Net Of Accretion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfStockByClassTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Stock by Class [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfStockByClassTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Stock By Class [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total investments at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Securities Available For Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2029 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Nine Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty nine notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net realized gains losses on investments and foreign currency translation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Realized Gains Losses on Investments and Foreign Currency Translation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net realized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized gains (losses) on investments and foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Future Realized Capital Gains Prior to April 1, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Future Realized Capital Gains Prior to April First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Future realized capital gains prior to April first two thousand fourteen.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of all remaining pre-incentive fee net investment income quarterly.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of All Remaining Pre Incentive Fee Net Investment Income Quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of all remaining pre-Incentive Fee net investment income quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre-incentive fee net investment income payable after hurdle rate reached and catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Payable After Hurdle Rate Reached And Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of pre-Incentive Fee net investment income payable in any quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Liabilities and Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ability to Raise Additional Capital Due to Regulation Governance On BDC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ability to Raise Additional Capital Due to Regulation Governance On BDC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instruments and Hedging Activities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Azurite Intermediate Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Azurite Intermediate Holdings, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Azurite Intermediate Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of offering and underwriting costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BaseDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Base dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BaseDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Base Dividend [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BaseDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reinvestment of dividends during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Available For Sale Securities [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ForeScout Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ForeScout Technologies, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ForeScoutTechnologiesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fore Scout Technologies Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Un-realized investment gains (losses).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Un Realized Investment Gains Losses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeeWaived_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Management and incentive fees waived (Note 3)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeeWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management and Incentive Fee Waived</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementAndIncentiveFeeWaived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Management and incentive fee waived.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidated Entities [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consolidated Entities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LucidworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lucidworks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LucidworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lucidworks Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LucidworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lucidworks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Interest Rate During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment owed on principal amount outstanding and accrued interest make whole amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment Owed On Principal Amount Outstanding And Accrued Interest Make Whole Amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owed On Principal Amount Outstanding And Accrued Interest Make whole Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetRealizedGainsTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undistributed net realized gains - tax basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetRealizedGainsTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Undistributed Net Realized Gains Tax Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetRealizedGainsTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Undistributed net realized gains tax basis.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Long-Term Debt Instruments [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance,Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares Outstanding, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Amount Available</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Remaining Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, remaining borrowing capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Borrow money which magnifies potential for gain or loss and increases risk of investing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Borrow Money Which Magnifies Potential for Gain or Loss and Increases Risk of Investing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Currency Transactions and Translations Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign Currency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Securities, FV-NI</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Equity Securities, FV-NI, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured Credit Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured credit investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetValuationWaterfallMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Asset valuation waterfall.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetValuationWaterfallMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Valuation Waterfall [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetValuationWaterfallMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Valuation Waterfall</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolver &amp; Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolver &amp; Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolver &amp; equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Paid in Capital in Excess of Par</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on January 31, 2025 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on January 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on January 31, 2025.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HornetsecurityHoldingGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hornetsecurity Holding GmbH</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HornetsecurityHoldingGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hornetsecurity Holding GMBH Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HornetsecurityHoldingGmbhMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hornetsecurity Holding GMBH.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Affiliation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Services Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialServicesSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of weighted cumulative realized capital gains less realized capital losses and unrealized capital losses through March 31, 2014 hurdle rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Weighted Cumulative Realized Capital Gains Less Realized Capital Losses and Unrealized Capital Losses Through March 31 2014 Hurdle Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of weighted cumulative realized capital gains less cumulative realized capital losses and unrealized capital losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in additional paid in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease in Additional Paid in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in additional paid in capital.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Components of Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Components Of Interest Expense [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of components of interest expense.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in accounting principle, accounting standards update, immaterial effect</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Level 3 Investments at Fair Value Significant Unobservable Inputs Used in Valuations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Offering Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Offering Expenses [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity offering expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt (net of deferred financing costs of $25,258 and $21,930, respectively)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Carrying value of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Outstanding debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Contract [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in incentive fees on net capital gains accrued to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Incentive Fees On Net Capital Gains Accrued To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains accrued to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherPayablesToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other payables to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherPayablesToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Payables To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherPayablesToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other payables to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeMaturityDates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Contract End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest from investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Date Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends date declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrealized gains (losses) on derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net change in unrealized (gains) losses on interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss) on Derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Adopted [true false]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_CA_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CANADA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_CA_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Canada</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Preferred Stock, Shares Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Preferred Stock, Shares Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes, 2024 Notes, 2026 Notes, 2028 Notes and 2029 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Twenty Four Twenty Six TwentyEight And Twenty Nine Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three twenty four twenty six twentyeight and twenty nine notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Investment Income Before Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Northeast.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Northeast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NortheastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - Northeast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DiscoParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disco Parent, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DiscoParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disco Parent Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DiscoParentIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disco parent Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Operating Capital [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset paid-in-kind interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Paid In Kind Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Paid-in-kind interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Business services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BusinessServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Business Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutomotiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Automotive.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutomotiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Automotive [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AutomotiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Automotive</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance, beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ability to enter into transactions with affiliates is restricted.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ability to Enter into Transactions with Affiliates is Restricted [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2028 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty eight notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Party Status [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksAssociatedWithChangesInInterestRatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Risks associated with changes in interest rates.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksAssociatedWithChangesInInterestRatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Risks Associated With Changes In Interest Rates [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksAssociatedWithChangesInInterestRatesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Risks Associated with Changes in Interest Rates [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TruckLiteCoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Truck-Lite Co.,LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TruckLiteCoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Truck-Lite Co.,LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TruckLiteCoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Truck-Lite Co.,LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionOriginalDebtAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Value of debt converted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionOriginalDebtAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion, Original Debt, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Insurance [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InsuranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Insurance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Geographical</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_US_lbl" xlink:role="http://www.xbrl.org/2003/role/label">UNITED STATES</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_US_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset net amortization of discount on securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Net Amortization Of Discount On Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net amortization of discount on securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Component of Carrying Value of Convertible Notes and Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Component Of Carrying Value Of Convertible Notes and Interest Rate [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of component of carrying value of convertible notes and interest rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Controlled, Affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Affiliated Issuer, Controlled [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Issuance Costs, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party, Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Information:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on june twelve two thousand and twenty eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity On June Twelve Two Thousand And Twenty Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on June 12, 2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates, interest income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HealthcareSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Healthcare Sector [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HealthcareSectorMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Healthcare</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Earnings per share basic and diluted line items.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic And Diluted [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings Per Share Basic And Diluted [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Distributable Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre incentive fee net investment income hurdle rate quarterly.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Hurdle Rate Quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of hurdle rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative, fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Derivative, Fair Value, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Fair Value, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Significant Accounting Policies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instruments and Hedging Activities Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlphaMidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Alpha Midco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlphaMidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alpha Midco Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlphaMidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Alpha Midco Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_AU_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AUSTRALIA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_AU_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Australia</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Forecast [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Forecast</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HotelGamingAndLeisureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hotel, Gaming and Leisure.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HotelGamingAndLeisureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hotel Gaming And Leisure [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HotelGamingAndLeisureMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hotel, Gaming and Leisure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignExchangeForwardMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign currency forward contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignExchangeForwardMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Exchange Forward [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement Inputs and Valuation Techniques [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis Valuation Techniques [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Commitments To Fund Investments In Current Portfolio Companies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Commitments To Fund Investments In Current Portfolio Companies [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of commitments to fund investments in current portfolio companies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Accounting Principle, Accounting Standards Update, Adoption Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in accounting principle, accounting standards update, adoption date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess pre-incentive fee net investment income, quarterly after catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Quarterly After Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess pre-Incentive Fee net investment income quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap one.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net realized (gains) losses on foreign currency transactions.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Realized (Gains) Losses on Foreign Currency Transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile increase (decrease) in net assets resulting from operations to net cash provided by (used in) operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reference Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Basis Spread, Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred financing costs and original issue discounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Tax Basis Components of Distributable Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Tax Basis Components Of Distributable Earnings [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of tax basis components of distributable earnings.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdjustmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdjustmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdjustmentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adjustments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlueSnapIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BlueSnap, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlueSnapIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Blue Snap Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlueSnapIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BlueSnap, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt Instrument, basis spread on variable rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Basis Spread on Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reference Rate and Spread percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net change in unrealized (gains) losses on foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Translation of other assets and liabilities in foreign currencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, par</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and Debt Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap three.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Three [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tango Management Consulting, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tango Management Consulting L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TangoManagementConsultingLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tango Management Consulting, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion, Converted Instrument, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, principal converted amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program, authorized amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchase Program, Authorized Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwaps_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swaps.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwaps_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwaps_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cash proceeds from issuance of common stock, net of underwriting fees and offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock, net of offering and underwriting costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BaseRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Base Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BaseRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Base Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosure, Asset and Liability, Not Measured at Fair Value [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Disclosure Asset And Liability Not Measured At Fair Value [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, $0.01 par value; 400,000,000 shares authorized, 92,785,806 and 88,493,749 shares issued, respectively; and 92,121,556 and 87,829,499 shares outstanding, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Convertible, Conversion Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, conversion price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Gain (Loss), Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Foreign currency transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxReclassificationOfStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax reclassification of stockholders' equity in accordance with GAAP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxReclassificationOfStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax reclassification of stockholders' equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxReclassificationOfStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Reclassification Of Stockholders Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtConversionPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt conversion principal amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtConversionPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DebtConversionPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt conversion principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Distribution to Shareholders, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deferred tax benefit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawRevolverPreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw, Revolver &amp; Preferred Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawRevolverPreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw Revolver &amp; Preferred Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawRevolverPreferredEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw revolver &amp; preferred equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income taxes, including excise taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">South.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">South [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SouthMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - South</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of non-qualifying assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Non Qualifying Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of non-qualifying assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of weighted cumulative realized capital gains less cumulative realized capital losses and unrealized capital losses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Weighted Cumulative Realized Capital Gains Less Cumulative Realized Capital Losses And Unrealized Capital Losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of weighted cumulative realized capital gains less cumulative realized capital losses and unrealized capital losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Cash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Cash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of securities as percentage of net assets in percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Of Securities As Percentage Of Net Assets In Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of securities as percentage of net assets in percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty four notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RetailAndConsumerProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Retail and Consumer Products.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RetailAndConsumerProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retail And Consumer Products [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RetailAndConsumerProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Retail and Consumer Products</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Input Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TRPAssetsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">TRP Assets, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TRPAssetsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">T R P Assets L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TRPAssetsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">TRP Assets, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net capital gains.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Capital Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Excise and other taxes paid during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Approach and Technique [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valuation Approach and Technique</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of securities as percentage of net assets amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Of Securities As Percentage Of Net Assets Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of securities as percentage of net assets amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of management fee in excess of annual rate on gross assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Management Fee In Excess Of Annual Rate On Gross Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of management fee in excess of annual rate on gross assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Due from Affiliates, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Aggregate Principal Amount Committed</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Effect, Period of Adoption, Adjustment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative Effect, Period of Adoption, Adjustment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BabylonFincoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Babylon Finco Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BabylonFincoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Babylon Finco Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BabylonFincoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Babylon finco limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Repayments of Short-Term Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments of Short-Term Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RepaymentsOfShortTermDebt_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments on debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Derivative notional amount held during period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Notional Amount Held during Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notional Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net realized and unrealized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Gain (Loss) on Investment, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty two convertible notes member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Two Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Convertible Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees accrued related to expense (reversal) capital gains fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees Accrued Related To Expense (Reversal) Capital Gains Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees accrued related to expense (reversal) of capital gains fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OutsystemsLuxcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">OutSystems Luxco SARL</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OutsystemsLuxcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Outsystems Luxco [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OutsystemsLuxcoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Outsystems Luxco.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other temporary differences</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Temporary Differences</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherTemporaryDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other temporary differences.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InternetServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Internet Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InternetServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Internet Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InternetServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Internet Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Taxable Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Taxable Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxableIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Taxable income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid, Excluding Capitalized Interest, Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest paid during the period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoninterestExpenseDirectorsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noninterest Expense Directors Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoninterestExpenseDirectorsFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Directors&#8217; fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment measurement input</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alternative Investment, Measurement Input</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap six.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Six [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSixMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Six</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Issuer Affiliation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Structured credit investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Structured Credit Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_StructuredCreditInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Structured credit investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Fair Value, Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Fair Value, Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total investments at fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility maximum borrowing capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on April 23, 2027 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on April 23, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on April 23, 2027.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Adjustment in carrying value result from hedge accounting</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain (loss) on fair value effective hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Fair Value Hedge, Included in Effectiveness, Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesRealizedAndPayableToAdvisor_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees realized and payable to advisor.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesRealizedAndPayableToAdvisor_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees Realized And Payable To Advisor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesRealizedAndPayableToAdvisor_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees realized and payable to advisor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IRGSEHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">IRGSE Holding Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IRGSEHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">I R G S E Holding Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IRGSEHoldingCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">IRGSE Holding Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FullsteamOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fullsteam Operations, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FullsteamOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fullsteam Operations LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FullsteamOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fullsteam Operations LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net investment income payable to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Investment Income Payable To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net investment income payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Incentive Fee to Average Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Portfolio turnover</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_LU_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Luxembourg</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_LU_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LUXEMBOURG</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Undistributed net investment income - tax basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Undistributed Net Investment Income - Tax Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Undistributed net investment income - tax basis.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NumberOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramExpirationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program, expiration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramExpirationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchase Program Expiration Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrdinaryIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ordinary Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrdinaryIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ordinary Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OrdinaryIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ordinary income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Investment Gains (Losses) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized gains (losses):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Change in Unrealized Gains or Losses on Investments for Which Level 3 Inputs were Used in Determining Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevolvingCreditFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetwrixCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Netwrix Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetwrixCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Netwrix Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetwrixCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Netwrix Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share-basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Manufacturing</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Manufacturing [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManufacturingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Manufacturing.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess pre-incentive fee net investment income for immediate preceding calendar quarter.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excess Pre Incentive Fee Net Investment Income For Immediate Preceding Calendar Quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess pre-incentive fee net investment income for immediate preceding calendar quarter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adviser.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adviser [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adviser</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaidInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Paid-in-kind interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaidInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Paid-In-Kind Interest Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaidInKindInterestIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Paid-in-kind interest income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies (Note 8)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes, 2026 Notes and 2028 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Four Twenty Six and Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Twenty Four Twenty Six and Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-controlled, non-affiliated investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Controlled Non Affiliated Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-controlled, Non-affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Investments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArtisanBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Artisan Bidco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArtisanBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Artisan Bidco, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArtisanBidcoIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Artisan Bidco, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Value of investment declines, management fee and incentive fee will be payable to adviser.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Value of Investment Declines, Management Fee and Incentive Fee will be payable to Adviser [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total increase/(decrease) in net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Net Asset Value Per Share, Period Increase (Decrease)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total increase/(decrease) in net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Input Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksAssociatedWithConflictsOfInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Risks Associated with Conflicts of Interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RisksAssociatedWithConflictsOfInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Risks Associated with Conflicts of Interest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Provided by (Used in) Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Weighted Average Interest Rate, over Time</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments Fair Value Disclosure Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsFairValueDisclosureNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments fair value disclosure net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in incentive fees on net investment income payable to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Incentive Fees On Net Investment Income Payable To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Incentive fees on net investment income payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Expense Ratio, Voluntary Fee Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ratio of net expenses to average net asset, excluding waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeDividend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeDividend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeDividend_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Dividend Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share-diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BCTO Ace Purchaser, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BCTO Ace Purchaser, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BCTOAcePurchaserIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">B C T O Ace Purchaser Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetUnrealizedGainsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net unrealized gains on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetUnrealizedGainsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Unrealized Gains on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetUnrealizedGainsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net unrealized gains on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sales Proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument, Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CurrentMarketPricePerSharePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of current market price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CurrentMarketPricePerSharePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Market Price Per Share Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CurrentMarketPricePerSharePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Current market price per share percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OilGasAndConsumableFuelsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Oil, Gas and Consumable Fuels.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OilGasAndConsumableFuelsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Oil Gas And Consumable Fuels [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OilGasAndConsumableFuelsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Oil, Gas and Consumable Fuels</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Industry Composition of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Industry Composition Of Investments At Fair Value [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of industry composition of investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PdiTaHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PDI TA Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PdiTaHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PDI TA Holdings, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PdiTaHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PDI TA Holdings, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Significant accounting policies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Instrument, Increase (Decrease), Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Increase (Decrease), Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in carrying value of notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Settlements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments / redemptions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net expense for federal excise tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Expense For Federal Excise Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTax_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net expense for federal excise tax.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Related Commitment Fees and Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitment fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Capital gains accrue following March 31, 2014.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Gains Accrue Following March Thirty First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Capital Gains Accrue Following March 31, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MezzanineDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mezzanine debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MezzanineDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mezzanine Debt Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MezzanineDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mezzanine Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Issuance And Repurchase Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company issuance and repurchase per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Net Assets, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Net Assets, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend declared from realized gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividend Declared From Realized Gains Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividend declared from realized gains per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock repurchase program period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Repurchase Program, Period in Force</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess catch-up provision for pre-incentive fee net investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excess Catch Up Provision For Pre Incentive Fee Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess catch-up provision for pre-Incentive Fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments owned estimated cost basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments Owned Estimated Cost Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments owned estimated cost basis.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Indebtedness could adversely affect business financial conditions or results of operations.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Indebtedness could Adversely Affect Business Financial Conditions or Results of Operations [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related and Nonrelated Party Status [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum percentage of voting securities in investment portfolio.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum Percentage Of Voting Securities In Investment Portfolio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum percentage of voting securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Three Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyThreeNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty three notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputDiscountRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Discount Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputDiscountRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OverAllotmentOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Over-Allotment Option [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OverAllotmentOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Overallotment Option</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net expense for federal excise tax and other taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Expense For Federal Excise Tax And Other Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net expense for U.S. federal excise tax and other taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HeritageEnvironmentalServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Heritage Environmental Services, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HeritageEnvironmentalServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Heritage Environmental Services, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HeritageEnvironmentalServicesIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Heritage environmental services, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Project44IncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Project44, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Project44IncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Project44 Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_Project44IncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Project44, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and Cash Equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per common share-basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary Of Financial Highlights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimeRevenueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PrimeRevenue, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimeRevenueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prime Revenue Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PrimeRevenueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PrimeRevenue, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Components</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Other Operating Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Operating Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments, Debt and Equity Securities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, stated maturity date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Stated Maturity Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, stated maturity date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared from net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends Declared From Net Investment Income Per Share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Declared From Net Investment Income Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022 Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Two Convertible Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty two convertible notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Agreement termination period, without penalty.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Agreement Termination Period Without Penalty</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreement termination period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Conversion, Converted Instrument, Shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt conversion, shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Designated as Hedging Instrument [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Designated As Hedging Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-controlled, affiliated investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Controlled Affiliated Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-controlled, Affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">West.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">West [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - West</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rapid Data GmbH Unternehmensberatung</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rapid Data GmbH Unternehmensberatung [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rapid Data GmbH Unternehmensberatung.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawRevolverEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw Revolver &amp; Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawRevolverEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw &amp; Revolver &amp; Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawRevolverEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed Draw &amp; Revolver &amp; Equity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityExtendedDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Line of credit facility, extended date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityExtendedDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line Of Credit Facility Extended Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LineOfCreditFacilityExtendedDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, extended date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Authority [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation and Presentation of Financial Statements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers into (out of) Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of net proceeds of sale of equity interests.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Net Proceeds Of Sale Of Equity Interests</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of net proceeds of sale of equity interests</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock, price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BctoBluebillBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BCTO Bluebill Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BctoBluebillBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BCTO Bluebill Buyer, Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BctoBluebillBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BCTO Bluebill Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlaskaBidcoOyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Alaska bidco oy member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlaskaBidcoOyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alaska Bidco Oy [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AlaskaBidcoOyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Alaska Bidco Oy</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase (decrease) in distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease in Distributable Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in distributable earnings.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Stated interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Stated Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Effect, Period of Adoption [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative Effect, Period of Adoption</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net Expense.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment advisory agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Advisory Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentAdvisoryAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Advisory Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanAchievementCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">American Achievement, Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanAchievementCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">American Achievement Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AmericanAchievementCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">American Achievement Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap ten.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Ten [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Ten</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends declared from distributable earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividends, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental dividend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Dividend [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SupplementalDividendMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Average Outstanding Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Average debt outstanding (in millions)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three and twenty four and twenty six notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three And Twenty Four And Twenty Six Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes, 2024 Notes and 2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments of Dividends, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDividends_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Dividends paid to stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 3 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Acquired, Average Cost Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring and Nonrecurring [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AccountingStandardsUpdate202206Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASU 2022-06</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AccountingStandardsUpdate202206Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update 2022-06 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AccountingStandardsUpdate202206Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accounting standards update 2022-06.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from settlements of interest rate swaps excluding upfront fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Settlements Of Interest Rate Swaps Excluding Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from settlements of interest rate swaps excluding upfront fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Reconciliation Increase in Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Reconciliation Increase In Net Assets [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of reconciliation increase in net assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reimbursement of Transaction-Related Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reimbursement Of Transaction Related Expenses [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reimbursement of transaction-related expenses.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysianFincoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Elysian Finco Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysianFincoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Elysian Finco Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ElysianFincoLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Elysian Finco Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other General and Administrative Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Rate Derivatives, at Fair Value, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Derivatives, at Fair Value, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Market Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Fair market value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Investments At Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfInvestmentsAtFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment fair value percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other general and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosure of Asset and Liability Not Measured at Fair Value [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Disclosure Of Asset And Liability Not Measured At Fair Value [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Chemicals.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Chemicals [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ChemicalsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Chemicals</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwelveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap twelve.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwelveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Twelve [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwelveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Twelve</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and Dividend Income Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and Dividend Income Recognition [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest and dividend income recognition.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Operating Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Operating Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap eight.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Eight [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapEightMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Eight</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Purchases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchases or originations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letter of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letter of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Denominator for basic weighted average shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average shares of common stock outstanding-basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Denominator for basic weighted average shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Settlement of 2022 Convertible Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Settlement of Convertible Notes Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company settlement of convertible notes per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvalaraIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Avalara, Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvalaraIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Avalara, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AvalaraIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Avalara, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss), Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Financing Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Flows from Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued in connection with dividend reinvestment plan, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of management fee calculated on gross assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Management Fee Calculated On Gross Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of management fee on gross assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of ordinary income qualified as interest related dividend exempt from US withholding tax applicable to non-US shareholder</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Ordinary Income Qualified as Interest Related Dividend Exempt from Domestic Withholding Tax Applicable to Foreign Shareholder</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of ordinary income qualified as interest related dividend exempt from domestic withholding tax applicable to foreign shareholder.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on extinguishment of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Extinguishment of Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Extinguishment of Debt, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kangaroo Bidco AS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kangaroo Bidco A S [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KangarooBidcoASMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kangaroo Bidco A S.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Related Party Transactions, by Related Party [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Related Party Transactions By Related Party [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum percentage of investment company taxable income distribute to stockholders in each taxable year to qualify as RIC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum Percentage Of Investment Company Taxable Income Distribute To Stockholders In Each Taxable Year To Qualify As R I C</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum percentage of investment company taxable income distribute to stockholders in each taxable year to qualify as RIC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative, basis spread on variable rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Basis Spread on Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates at fair value net change in unrealized gain (loss).</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Net Change in Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Change in Unrealized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_GB_lbl" xlink:role="http://www.xbrl.org/2003/role/label">UNITED KINGDOM</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_GB_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United Kingdom</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetAssetLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Fair Value, Net Asset (Liability), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetAssetLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Net Asset (Liability)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetAssetLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net assets, end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NondesignatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">No Longer Designated As Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NondesignatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Not Designated As Hedging Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NondesignatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Not Designated as Hedging Instrument [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreements and Related Party Transactions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gain loss form adjustment of Paid-in-kind interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain Loss form Adjustment of Paid-in-kind Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Paid-in-kind interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of an effective hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value of an effective hedge.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueOfAnEffectiveHedge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Of An Effective Hedge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value of Company's 2024 Notes, 2026 Notes, 2028 Notes and 2029 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Carrying Values and Estimated Fair Values of Debt Instruments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments of Financing Costs, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Financing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Nondeductible federal excise tax percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nondeductible Federal Excise Tax Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Nondeductible U.S. federal excise tax percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Transportation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Transportation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TransportationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transportation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_FI_lbl" xlink:role="http://www.xbrl.org/2003/role/label">FINLAND</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_FI_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finland</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchases and originations of investments, net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchases And Originations Of Investments Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases and originations of investments, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cost of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Technique Cost of Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Valuation Technique Cost of Investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverAndPartnershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolver &amp; Partnership Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverAndPartnershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolver And Partnership Interest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolverAndPartnershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolver and partnership interest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transfers within Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement With Unobservable Inputs Reconciliation Recurring Basis Asset Transfers Within Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair value measurement with unobservable inputs reconciliation recurring basis asset transfers within level 3.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment due date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment due date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Due Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ObligorGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Obligor Group [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ObligorGroupMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Obligor Group</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated gross unrealized loss on tax cost investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estimated Gross Unrealized Loss on Tax Cost Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Estimated gross unrealized loss on tax cost investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letters of Credit Outstanding, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LettersOfCreditOutstandingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of letters of credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repayments on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Repayments on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Repayments On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RepaymentsOnInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayments on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiscalPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fiscal Period, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FiscalPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fiscal Year End</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cumulative Effect, Period of Adoption [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cumulative Effect, Period of Adoption</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unrealized loss on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Loss On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized losses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre-incentive fee net investment income, annualized after catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Annualized After Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of pre-Incentive Fee net investment income annualized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial and Derivative Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivatives, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementFeeWaiverHurdle_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Management fee waiver hurdle.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementFeeWaiverHurdle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Waiver Hurdle</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ManagementFeeWaiverHurdle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of asset coverage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued in connection with dividend reinvestment plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents (restricted cash of $29,100 and $23,979, respectively)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, at Carrying Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Realized Investment Gains (Losses), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Investment Gains (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized gains (losses) on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RealizedInvestmentGainsLosses_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Realized loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accretion (Amortization) of Discounts and Premiums, Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net amortization of discount on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GalileoParentincMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Galileo ParentInc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GalileoParentincMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Galileo Parent, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_GalileoParentincMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Galileo Parent Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeverageWaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Leverage waiver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeverageWaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leverage Waiver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeverageWaiverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leverage Waiver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PartnershipInterestOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Partnership/Membership interest of ownership</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PartnershipInterestOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Partnership Interest Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PartnershipInterestOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Partnership interest ownership percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradingSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Trading</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TradingSecuritiesDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EdgeBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Edge Bidco B.V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EdgeBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Edge Bidco B V [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EdgeBidcoBVMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Edge Bidco B.V.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Conversion of convertible notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued upon conversion of convertible notes, value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Conversion of Convertible Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Debt [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Debt Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfessionalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Professional Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfessionalFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Professional fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Balance, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury stock at cost; 664,250 and 664,250 shares held, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Treasury stock at cost; [664,250] and 664,250 shares held, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Treasury Stock, Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Controlled, affiliated investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Controlled Affiliated Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ControlledAffiliatedInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Controlled, Affiliated Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates at fair value net realized gain loss.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Realized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Gain/(Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Selling, General and Administrative Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Selling, General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expenses incurred</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Swap settlement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Swap settlement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Swap Settlement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SwapSettlement_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Swap settlement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AsgIiLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ASG II, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AsgIiLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ASG II, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AsgIiLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASG II, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayableFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notes Payable, Fair Value Disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayableFairValueDisclosure_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">BTRS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BtrsHolding Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BTRS Holding Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BtrsHoldingIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BTRS Holding Inc. [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxCostOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax cost of investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxCostOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Cost of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TaxCostOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax cost of investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of minimum qualifying assets to purchase non-qualifying assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Minimum Qualifying Assets To Purchase Non Qualifying Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of minimum qualifying assets to purchase non qualifying assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ExtinguishmentOfDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Extinguishment of Debt, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ExtinguishmentOfDebtAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Extinguishment of debt, amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HippoXpaBidcoAbMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hippo XPA Bidco AB</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HippoXpaBidcoAbMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hippo XPA Bidco AB [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HippoXpaBidcoAbMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hippo XPA Bidco AB</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">EMS Linq, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">EMS Linq, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EMSLinqIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">E M S Linq Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Second-lien debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Second Lien Debt Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SecondLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Second-lien Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments in and advances to affiliates, other income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net investment income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Incentive fees realized and payable to advisor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 Notes, 2024 Notes, 2026 Notes and 2028 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three Twenty Four Twenty Six And Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty three twenty four twenty six and twenty eight notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for settlements of interest rate swaps excluding upfront fees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Settlements Of Interest Rate Swaps Excluding Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for settlements of interest rate swaps excluding upfront fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Federal Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DomesticCountryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Domestic Tax Authority [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap two.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DistributedEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total distributable earnings - book basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DistributedEarnings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Distributed Earnings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PerShareMarketValueAtEndPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Per Share Market Value At End Period.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PerShareMarketValueAtEndPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Per Share Market Value At End Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PerShareMarketValueAtEndPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Per share market value at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on April 24, 2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity On April 24, 2029 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on April 24, 2029.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsAtFairValueTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsAtFairValueTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments At Fair Value [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentsAtFairValueTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net change in unrealized gains (losses) on investments and foreign currency translation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net unrealized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net unrealized (gains) losses on investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net change in unrealized gains (losses) on investments and foreign currency translation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Change In Unrealized Gains Losses On Investments And Foreign Currency Translation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total net change in unrealized gains (losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Notes Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notes Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding Principal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Industry Sector [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Industry Sector</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Interest Rate at Period End</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, base rate percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Designation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Designation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares repurchased</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Shares, Acquired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockSharesAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Purchases of treasury stock, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeeAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Commitment Fee Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeeAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility commitment fee amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Emerging Growth Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchaseCommitmentToFundInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Purchase commitment to fund investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchaseCommitmentToFundInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Purchase Commitment To Fund Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PurchaseCommitmentToFundInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Portfolio Company Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, before Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrealized and Realized Gains (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MarketApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation, Market Approach [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MarketApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Market Multiple</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of management fee in excess of quarter rate on gross assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Management Fee in Excess of Quarter Rate on Gross Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of management fee in excess of quarter rate on gross assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherBookTaxDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other book-tax differences</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherBookTaxDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Book-tax Differences</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherBookTaxDifferences_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other book-tax differences.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OfficeProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Office Products.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OfficeProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Office Products [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OfficeProductsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Office Products</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis of Accounting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommunicationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Communications.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommunicationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Communications [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CommunicationsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Communications</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss) from Operations, Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated gross unrealized gains on tax cost investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Estimated Gross Unrealized Gains on Tax Cost Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Estimated gross unrealized gains on tax cost investment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Derivative, Gain (Loss) on Derivative, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative, Gain (Loss) on Derivative, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in Unrealized Gains / (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in Fair Value of Investments Using Level 3 Inputs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of excess pre-incentive fee net investment income payable after hurdle rate reached and catch-up achieved.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Excess Pre Incentive Fee Net Investment Income Payable After Hurdle Rate Reached And Catch Up Achieved</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of excess pre-Incentive Fee net investment income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApteanIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aptean Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApteanIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aptean Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ApteanIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aptean Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Expiration Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, expiration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of capital gains from April 1, 2024 hurdle rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Capital Gains From April 1 2024 Hurdle Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of incentive fee rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pledged Status [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pledged Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred tax asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Tax Assets, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredTaxAssetsGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Tax Assets, Gross, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ExtraHopNetworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ExtraHop Networks, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ExtraHopNetworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Extra Hop Networks Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ExtraHopNetworksIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ExtraHop Networks Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity and Other Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity and other investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity And Other Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized capital gains accrued beginning April 1, 2014.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Capital Gains Accrued Beginning April First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Capital Gains Accrued Beginning April 1, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdditionalAggregatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Additional aggregate principal amount.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdditionalAggregatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Aggregate Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdditionalAggregatePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional aggregate principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AxonifyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Axonify, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AxonifyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Axonify Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AxonifyIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Axonify, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_DE_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Germany</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_DE_lbl" xlink:role="http://www.xbrl.org/2003/role/label">GERMANY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PassportLabsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Passport Labs, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PassportLabsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Passport Labs Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PassportLabsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Passport Labs, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gross Reductions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Offsetting Assets and Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Offsetting Assets And Liabilities [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Offsetting assets and liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends to Common Stockholders</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap seven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Seven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapSevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Seven</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, $0.01 par value; 100,000,000 shares authorized; no shares issued and outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">First-lien debt investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">First Lien Debt Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_FirstLienDebtInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">First-lien Debt Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends Payable [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Unused Capacity, Commitment Fee Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit facility, undrawn amount percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Net realized (gains) losses on interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Realized gains (losses) on derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Sale of Derivatives</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfDerivatives_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate swaps</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Initial Acquisition Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentAcquisitionDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Acquisition Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Earnings per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of pre-incentive fee net investment income payable quarterly.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Pre Incentive Fee Net Investment Income Payable Quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of total pre-Incentive fee net investment income payable quarterly</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Income [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other income.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity and other investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity And Other Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EquityAndOtherInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity and other investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Erling Lux Bidco SARL.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Erling Lux Bidco SARL [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Erling Lux Bidco SARL</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ErlingLuxBidcoSarlMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Erling Lux Bidco Sarl</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation, Income Approach [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Approach</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IssuanceOfCommonStockNetOfOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IssuanceOfCommonStockNetOfOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of Common Stock Net of Offering Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IssuanceOfCommonStockNetOfOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock net of offering costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restricted Cash, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenNevisMidcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ben Nevis Midco Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenNevisMidcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ben Nevis Midco Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BenNevisMidcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ben nevis midco limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Financial Highlights [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Highlights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BayshoreIntermediate2LPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bayshore Intermediate #2, L.P.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BayshoreIntermediate2LPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bayshore Intermediate2 L P [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BayshoreIntermediate2LPMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bayshore Intermediate #2, LP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes, Including Excise Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Including Excise Taxes [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Income taxes, including excise taxes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fee Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncentiveFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accretion of Original issue Discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Discount (Premium)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of discount on debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap eleven.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Eleven [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapElevenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Eleven</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrewlineBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Crewline Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrewlineBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Crewline Buyer, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CrewlineBuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Crewline Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDeclaredTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Dividends Declared</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsDeclaredTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Declared [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Increase (decrease) in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase in net assets resulting from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Net Assets Resulting from Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Realized capital gains accrued prior to March 31, 2014.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Realized Capital Gains Accrued Prior To March Thirty First Two Thousand Fourteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Realized Capital Gains Accrued Prior to March 31, 2014</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfIncentiveFeeRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fee rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfIncentiveFeeRate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of incentive fee rate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PercentageOfIncentiveFeeRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Incentive Fee Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Financing Receivable [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Financing Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends Payable [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw &amp; Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw &amp; Equity [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawEquityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw &amp; equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Principal amount of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Debt, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding Principal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company, Investment Income (Loss) Ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ratio of net investment income to average net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of treasury stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Value, Acquired, Cost Method</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Offset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash collateral</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Financing Receivable [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Financing Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Management Fee Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ManagementFeeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesIndustryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Industry Sector [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquitySecuritiesIndustryMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Industry Sector</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredOrganizationCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred organization costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredOrganizationCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Organization Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DeferredOrganizationCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Deferred organization costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LegislationAllowsToIncurAdditionalLeverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Legislation allows to incur additional leverage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LegislationAllowsToIncurAdditionalLeverageMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Legislation Allows to Incur Additional Leverage [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty six notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Six Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentTypeCategorizationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Shares Newly Issued to Shareholders Who Have Not Opted Out of Dividend Reinvestment Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary of Shares Newly Issued to Shareholders Who Have Not Opted Out of Dividend Reinvestment Plan [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of shares newly issued to shareholders who have not opted out of dividend reinvestment plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowbuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ArrowBuyer, Inc. Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowbuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Arrow Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ArrowbuyerIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Arrow Buyer, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Treasury Stock, Common [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TreasuryStockCommonMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Treasury Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestRateSwapMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income for tax purposes, not book</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Income For Tax Purposes, Not Book</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other income for tax purposes, not book.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit, outstanding amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Line of Credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCredit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-Term Line of Credit, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of earnings per share basic and diluted table.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Earnings Per Share Basic And Diluted [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Earnings Per Share Basic And Diluted [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other expenses not currently deductible</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Expenses Not Currently Deductible</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other expenses not currently deductible.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2029 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Nine Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyNineNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty nine notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativesOffsettingFairValueAmountsPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Offsetting Assets and Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativesOffsettingFairValueAmountsPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivatives, Offsetting Fair Value Amounts, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TaxCreditCarryforwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax Credit Carryforward [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cordance Operations, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cordance Operations LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CordanceOperationsLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cordance Operations, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax provision</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gains Losses On Income Tax Provision</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unrealized gains losses on income tax provision.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments in and Advances to Affiliates, at Fair Value, Gross Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EducationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Education.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EducationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Education [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EducationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Education</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Geographic Composition of Investments at Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Geographic Composition Of Investments At Fair Value [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of geographic composition of investments at fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnfundedLoanCommitmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unfunded Loan Commitment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnfundedLoanCommitmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unfunded Loan Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap five.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Five [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapFiveMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ReliaQuest Holdings, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Relia Quest Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ReliaQuestHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ReliaQuest Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarcuraEquitiesLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Marcura Equities LTD</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarcuraEquitiesLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Marcura Equities LTD [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarcuraEquitiesLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Marcura Equities LTD.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Asset coverage percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Coverage Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AssetCoveragePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset coverage percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeantaasHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">LeanTaaS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeantaasHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LeanTaaS Holdings Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LeantaasHoldingsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LeanTaaS Holdings, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2028 Notes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Eight Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwoThousandTwentyEightNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty eight notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares, outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NO_lbl" xlink:role="http://www.xbrl.org/2003/role/label">NORWAY</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_NO_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Norway</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Midwest.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Midwest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MidwestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">United States - Midwest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on market value with reinvestment of dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Return Based On Market Value With Reinvestment Of Dividends.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Return Based On Market Value With Reinvestment Of Dividends</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EDBParentLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">EDB Parent, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EDBParentLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">E D B Parent L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EDBParentLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">EDB Parent, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in interest receivable paid-in-kind.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Interest Receivable Paid In Kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest receivable paid-in-kind</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIdentifierAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment, Identifier [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap nine.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Nine [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapNineMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Nine</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCommitment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Commitment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCommitment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Commitment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCommitment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock issued upon conversion of convertible notes, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Conversion of Convertible Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Conversion of convertible notes, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnNetAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total return based on net asset value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnNetAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Return Based On Net Asset Value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TotalReturnBasedOnNetAssetValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Return Based On Net Asset Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Quarterly Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Administration agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Administration Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_AdministrationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Administration Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase decrease in management fees payable to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Management Fees Payable To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Management fees payable to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid expenses and other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkylarkUkDebtcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SkyLark UK DebtCo Limited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkylarkUkDebtcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Skylark Uk Debtco Limited [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SkylarkUkDebtcoLimitedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SkyLark UK DebtCo Limited.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Asset Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Net asset value, beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetAssetValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Net Asset Value, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CostModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cost model.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CostModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost Model [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CostModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost Model</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Notional amount of interest rate swap</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Notional Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeNotionalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Notional value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Tax Character of Shareholder Distributions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Tax Character Of Shareholder Distributions [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of tax character of shareholder distributions.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront (Payments) / Receipts in derivative assets and liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Payments Receipts In Derivative Assets And Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront (Payments) / Receipts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlackScholesModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Black Scholes model.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlackScholesModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Black Scholes Model [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_BlackScholesModelMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Black Scholes Model</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided by (Used in) Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Cash Provided by (Used in) Financing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarketingServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Marketing Services.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarketingServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Marketing Services [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_MarketingServicesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Marketing Services</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pledged Status [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PledgedStatusAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pledged Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-Cash Financing Activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Unrealized gain on investments.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unrealized Gain On Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_UnrealizedGainOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross unrealized gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revolving Credit Facility Maturity on February 4, 2026 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revolving Credit Facility Maturity on February 4, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revolving credit facility maturity on February 4, 2026,</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accrued Interest Receivable, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Rate [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableRateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndRevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed draw and revolver.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndRevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw And Revolver [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndRevolverMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw &amp; Revolver</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LongTermCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long Term Capital Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LongTermCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Capital Gains</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LongTermCapitalGains_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Long-term capital gains.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Hedge, Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Investment Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employment Hero Holdings Pty Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employment Hero Holdings Pty Ltd [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employment Hero Holdings Pty Ltd.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt instrument, description of variable rate basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Description of Variable Rate Basis</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reference Rate and Spread</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LaramieEnergyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Laramie Energy, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LaramieEnergyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Laramie Energy L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_LaramieEnergyLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Laramie Energy LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SOFR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dye &amp; Durham Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dye Durham Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DyeDurhamCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dye &amp; Durham Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Date to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SlBuyerCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">SL Buyer Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SlBuyerCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">SL Buyer Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SlBuyerCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SL Buyer Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidated Entities [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidatedEntitiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consolidated Entities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CoupaHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Coupa Holdings, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CoupaHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Coupa Holdings L L C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_CoupaHoldingsLLCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Coupa Holdings LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ThreeMonthLiborMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Three month libor.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ThreeMonthLiborMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Three Month Libor [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ThreeMonthLiborMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LIBOR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repurchase of debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Company Repurchase of Debt Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Investment company repurchase of debt per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Incentive fees on net capital gains accrued to affiliate.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Incentive Fees On Net Capital Gains Accrued To Affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incentive fees on net capital gains accrued to affiliate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income (Expense) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt and Equity Securities, Unrealized Gain (Loss), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt and Equity Securities, Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Unrealized Gain (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_SignificantAccountingPoliciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Significant accounting policies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KyribaCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Kyriba Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KyribaCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Kyriba Corp [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_KyribaCorpMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Kyriba Corp.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableNature_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DividendsPayableNature_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable, Nature</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Derivative Instruments [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Amounts Paid and Received on Interest Rate Swap Transactions, Excluding Upfront Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndMembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Delayed Draw and Membership Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndMembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Delayed Draw and Membership Interest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DelayedDrawAndMembershipInterestMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Delayed Draw and Membership Interest [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Input, Comparability Adjustment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Comparable Multiple</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends date shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Dividends payable date of shares issued day month and year.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends Payable Date Of Shares Issued Day Month And Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Four Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentyFourNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty four notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WranglerTopcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Wrangler TopCo, LLC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WranglerTopcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Wrangler TopCo, LLC [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_WranglerTopcoLlcMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Wrangler TopCo, LLC.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Denominator for diluted weighted average shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average shares of common stock outstanding-diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Credit Facility [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CreditFacilityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Credit Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ping Identity Holding Corp</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ping Identity Corporation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_PingIdentityCorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ping Identity Corporation.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares issued, price per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HirevueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Hirevue, inc member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HirevueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hirevue, Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_HirevueIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hirevue, Inc.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Investment percent of net assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Net Assets, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of Net Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Debt Securities, Available-for-Sale, Amortized Cost, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Use of Estimates, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Use of Estimates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThirteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate swap thirteen.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThirteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate Swap Thirteen [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_InterestRateSwapThirteenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest Rate Swap Thirteen</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026 Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty Six Notes [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_TwentyTwentySixNotesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Twenty twenty six notes.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Earnings Per Share, Basic and Diluted [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computation of Basic and Diluted Earnings Per Common Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Valuation Approach and Technique [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ValuationTechniqueAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Valuation Approach and Technique</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxAuthorityAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Authority [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current tax expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Current Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Hierarchy and NAV</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss), Investment and Derivative, Operating, and Foreign Currency Transaction, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Net Unrealized and Realized Gains (Losses)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for (Proceeds from) Hedge, Investing Activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Hedging Designation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_HedgingDesignationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Hedging Designation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from investments, net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Investments Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_ProceedsFromInvestmentsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from investments, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of debt, net of underwriting discount, offering costs and original issue discount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Unsecured Notes Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="tslx_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of offering and underwriting costs, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Debt investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AlternativeInvestment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alternative Investment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Including Disposal Group and Discontinued Operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, Cash Equivalents, and Restricted Cash, End of Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, cash equivalents, and restricted cash, beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetPledgedAsCollateralMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Pledged as Collateral [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetPledgedAsCollateralMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset Pledged as Collateral</link:label>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentTransitionReport" xlink:to="dei_DocumentTransitionReport_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapFourMember" xlink:to="tslx_InterestRateSwapFourMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" xlink:to="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" xlink:to="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromHedgeInvestingActivities" xlink:to="us-gaap_ProceedsFromHedgeInvestingActivities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsPayableAmountPerShare" xlink:to="us-gaap_DividendsPayableAmountPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_HumanResourceSupportServicesMember" xlink:to="tslx_HumanResourceSupportServicesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" xlink:to="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_StatementGeographicalAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IbisIntermediateCoMember" xlink:to="tslx_IbisIntermediateCoMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" xlink:to="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrealizedGainLossOnInvestments" xlink:to="us-gaap_UnrealizedGainLossOnInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentOwnedAtCost" xlink:to="us-gaap_InvestmentOwnedAtCost_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" xlink:to="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueInputsLevel1Member" xlink:to="us-gaap_FairValueInputsLevel1Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation" xlink:to="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_WeightedAverageMember" xlink:to="srt_WeightedAverageMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:to="us-gaap_ValuationTechniqueDiscountedCashFlowMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosuresTextBlock" xlink:to="us-gaap_FairValueDisclosuresTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" xlink:to="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromShortTermDebt" xlink:to="us-gaap_ProceedsFromShortTermDebt_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BearOpCoLLCMember" xlink:to="tslx_BearOpCoLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TotalReturnBasedOnMarketValue" xlink:to="tslx_TotalReturnBasedOnMarketValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_SE" xlink:to="country_SE_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock" xlink:to="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DividendsDeclaredDuringThePeriod" xlink:to="tslx_DividendsDeclaredDuringThePeriod_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolverMember" xlink:to="tslx_RevolverMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentInterestRatePaidInKind" xlink:to="us-gaap_InvestmentInterestRatePaidInKind_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RatioOfIndebtednessToNetCapital1" xlink:to="us-gaap_RatioOfIndebtednessToNetCapital1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsTextBlock" xlink:to="us-gaap_SubsequentEventsTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNonoperatingIncome" xlink:to="us-gaap_OtherNonoperatingIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BanyanSoftwareHoldingsLlcMember" xlink:to="tslx_BanyanSoftwareHoldingsLlcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:to="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_NL" xlink:to="country_NL_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" xlink:to="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OriginalIssueDiscountNetOfAccretion" xlink:to="tslx_OriginalIssueDiscountNetOfAccretion_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_ScheduleOfStockByClassTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentsFairValueDisclosure" xlink:to="us-gaap_InvestmentsFairValueDisclosure_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyNineNotesMember" xlink:to="tslx_TwoThousandTwentyNineNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" xlink:to="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" xlink:to="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_ClassOfStockLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsAbstract" xlink:to="us-gaap_RelatedPartyTransactionsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" xlink:to="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressStateOrProvince" xlink:to="dei_EntityAddressStateOrProvince_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:to="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AzuriteIntermediateHoldingsIncMember" xlink:to="tslx_AzuriteIntermediateHoldingsIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BaseDividendMember" xlink:to="tslx_BaseDividendMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_TradingSymbol" xlink:to="dei_TradingSymbol_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ForeScoutTechnologiesIncMember" xlink:to="tslx_ForeScoutTechnologiesIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsAxis" xlink:to="us-gaap_DividendsAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="tslx_UnRealizedInvestmentGainsLossesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ManagementAndIncentiveFeeWaived" xlink:to="tslx_ManagementAndIncentiveFeeWaived_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="srt_ConsolidatedEntitiesDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LucidworksIncMember" xlink:to="tslx_LucidworksIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:to="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" xlink:to="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UndistributedNetRealizedGainsTaxBasis" xlink:to="tslx_UndistributedNetRealizedGainsTaxBasis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesOutstanding" xlink:to="us-gaap_SharesOutstanding_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" xlink:to="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:to="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" xlink:to="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressCityOrTown" xlink:to="dei_EntityAddressCityOrTown_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_RelatedPartyTransactionLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_StructuredCreditInvestmentsMember" xlink:to="tslx_StructuredCreditInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureTextBlock" xlink:to="us-gaap_DebtDisclosureTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AssetValuationWaterfallMember" xlink:to="tslx_AssetValuationWaterfallMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolverEquityMember" xlink:to="tslx_RevolverEquityMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventMember" xlink:to="us-gaap_SubsequentEventMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" xlink:to="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_HornetsecurityHoldingGmbhMember" xlink:to="tslx_HornetsecurityHoldingGmbhMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancialServicesSectorMember" xlink:to="us-gaap_FinancialServicesSectorMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" xlink:to="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncreaseDecreaseInAdditionalPaidInCapital" xlink:to="tslx_IncreaseDecreaseInAdditionalPaidInCapital_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock" xlink:to="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="us-gaap_StatementOfStockholdersEquityAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DelayedDrawMember" xlink:to="tslx_DelayedDrawMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentMaturityDate" xlink:to="us-gaap_DebtInstrumentMaturityDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EquityOfferingExpensesPolicyTextBlock" xlink:to="tslx_EquityOfferingExpensesPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebt" xlink:to="us-gaap_LongTermDebt_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_DerivativeContractTypeDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:to="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherPayablesToAffiliate" xlink:to="tslx_OtherPayablesToAffiliate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ManagementFeePayable" xlink:to="us-gaap_ManagementFeePayable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeMaturityDates" xlink:to="us-gaap_DerivativeMaturityDates_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIncomeInterest" xlink:to="us-gaap_InvestmentIncomeInterest_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:to="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="srt_ScenarioUnspecifiedDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockCommonShares" xlink:to="us-gaap_TreasuryStockCommonShares_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnrealizedGainLossOnDerivatives" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_CA" xlink:to="country_CA_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyMember" xlink:to="us-gaap_RelatedPartyMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesOutstanding" xlink:to="us-gaap_PreferredStockSharesOutstanding_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityTaxIdentificationNumber" xlink:to="dei_EntityTaxIdentificationNumber_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NortheastMember" xlink:to="tslx_NortheastMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DiscoParentIncMember" xlink:to="tslx_DiscoParentIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BusinessServicesMember" xlink:to="tslx_BusinessServicesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AutomotiveMember" xlink:to="tslx_AutomotiveMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" xlink:to="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwentyTwentyEightNotesMember" xlink:to="tslx_TwentyTwentyEightNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RisksAssociatedWithChangesInInterestRatesMember" xlink:to="tslx_RisksAssociatedWithChangesInInterestRatesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TruckLiteCoLlcMember" xlink:to="tslx_TruckLiteCoLlcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionOriginalDebtAmount1" xlink:to="us-gaap_DebtConversionOriginalDebtAmount1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InsuranceMember" xlink:to="tslx_InsuranceMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeInstrumentRiskAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_SegmentGeographicalDomain" xlink:to="srt_SegmentGeographicalDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Assets" xlink:to="us-gaap_Assets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_US" xlink:to="country_US_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIncomeNet" xlink:to="us-gaap_InvestmentIncomeNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" xlink:to="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredFinanceCostsNet" xlink:to="us-gaap_DeferredFinanceCostsNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_RelatedPartyDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" xlink:to="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_HealthcareSectorMember" xlink:to="us-gaap_HealthcareSectorMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:to="tslx_EarningsPerShareBasicAndDilutedLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsMember" xlink:to="us-gaap_RetainedEarningsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeFairValueOfDerivativeNet" xlink:to="us-gaap_DerivativeFairValueOfDerivativeNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SignificantAccountingPoliciesTextBlock" xlink:to="us-gaap_SignificantAccountingPoliciesTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AlphaMidcoIncMember" xlink:to="tslx_AlphaMidcoIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_AU" xlink:to="country_AU_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ScenarioForecastMember" xlink:to="srt_ScenarioForecastMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_HotelGamingAndLeisureMember" xlink:to="tslx_HotelGamingAndLeisureMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignExchangeForwardMember" xlink:to="us-gaap_ForeignExchangeForwardMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" xlink:to="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_EquityComponentDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapOneMember" xlink:to="tslx_InterestRateSwapOneMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" xlink:to="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentBasisSpreadVariableRate" xlink:to="us-gaap_InvestmentBasisSpreadVariableRate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtDisclosureAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock" xlink:to="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_AdjustmentsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BlueSnapIncMember" xlink:to="tslx_BlueSnapIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCurrentReportingStatus" xlink:to="dei_EntityCurrentReportingStatus_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtPolicyTextBlock" xlink:to="us-gaap_DebtPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:to="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="us-gaap_InterestAndDebtExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapThreeMember" xlink:to="tslx_InterestRateSwapThreeMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TangoManagementConsultingLLCMember" xlink:to="tslx_TangoManagementConsultingLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionConvertedInstrumentAmount1" xlink:to="us-gaap_DebtConversionConvertedInstrumentAmount1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:to="us-gaap_StockRepurchaseProgramAuthorizedAmount1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_AssetsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwaps" xlink:to="tslx_InterestRateSwaps_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BaseRateMember" xlink:to="us-gaap_BaseRateMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:to="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:to="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CurrentFiscalYearEndDate" xlink:to="dei_CurrentFiscalYearEndDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TaxReclassificationOfStockholdersEquity" xlink:to="tslx_TaxReclassificationOfStockholdersEquity_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DebtConversionPrincipalAmount" xlink:to="tslx_DebtConversionPrincipalAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:to="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:to="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DelayedDrawRevolverPreferredEquityMember" xlink:to="tslx_DelayedDrawRevolverPreferredEquityMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxExpenseBenefit" xlink:to="us-gaap_IncomeTaxExpenseBenefit_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SouthMember" xlink:to="tslx_SouthMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfNonQualifyingAssets" xlink:to="tslx_PercentageOfNonQualifyingAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" xlink:to="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Cash" xlink:to="us-gaap_Cash_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyFourNotesMember" xlink:to="tslx_TwoThousandTwentyFourNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RetailAndConsumerProductsMember" xlink:to="tslx_RetailAndConsumerProductsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputTypeDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TRPAssetsLLCMember" xlink:to="tslx_TRPAssetsLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncentiveFeesOnNetCapitalGains" xlink:to="tslx_IncentiveFeesOnNetCapitalGains_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxesPaid" xlink:to="us-gaap_IncomeTaxesPaid_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_ValuationTechniqueDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" xlink:to="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent" xlink:to="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFaceAmount" xlink:to="us-gaap_DebtInstrumentFaceAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerSharePolicyTextBlock" xlink:to="us-gaap_EarningsPerSharePolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BabylonFincoLimitedMember" xlink:to="tslx_BabylonFincoLimitedMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfShortTermDebt" xlink:to="us-gaap_RepaymentsOfShortTermDebt_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DerivativeNotionalAmountHeldDuringPeriod" xlink:to="tslx_DerivativeNotionalAmountHeldDuringPeriod_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:to="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" xlink:to="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpensesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OutsystemsLuxcoMember" xlink:to="tslx_OutsystemsLuxcoMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherTemporaryDifferences" xlink:to="tslx_OtherTemporaryDifferences_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventsAbstract" xlink:to="us-gaap_SubsequentEventsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InternetServicesMember" xlink:to="tslx_InternetServicesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TaxableIncome" xlink:to="tslx_TaxableIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:to="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestPaidNet" xlink:to="us-gaap_InterestPaidNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoninterestExpenseDirectorsFees" xlink:to="us-gaap_NoninterestExpenseDirectorsFees_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AlternativeInvestmentMeasurementInput" xlink:to="us-gaap_AlternativeInvestmentMeasurementInput_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapSixMember" xlink:to="tslx_InterestRateSwapSixMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_LiabilitiesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_StructuredCreditInvestments" xlink:to="tslx_StructuredCreditInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentOwnedAtFairValue" xlink:to="us-gaap_InvestmentOwnedAtFairValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolvingCreditFacilityMaturityOnApril232027Member" xlink:to="tslx_RevolvingCreditFacilityMaturityOnApril232027Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" xlink:to="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncentiveFeesRealizedAndPayableToAdvisor" xlink:to="tslx_IncentiveFeesRealizedAndPayableToAdvisor_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IRGSEHoldingCorpMember" xlink:to="tslx_IRGSEHoldingCorpMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FullsteamOperationsLlcMember" xlink:to="tslx_FullsteamOperationsLlcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareAbstract" xlink:to="us-gaap_EarningsPerShareAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:to="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_LU" xlink:to="country_LU_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_LossContingenciesTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UndistributedNetInvestmentIncomeTaxBasis" xlink:to="tslx_UndistributedNetInvestmentIncomeTaxBasis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_AccountingPoliciesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NumberOfInvestments" xlink:to="tslx_NumberOfInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockRepurchaseProgramExpirationDate" xlink:to="us-gaap_StockRepurchaseProgramExpirationDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OrdinaryIncome" xlink:to="tslx_OrdinaryIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_StatementScenarioAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyThreeNotesMember" xlink:to="tslx_TwoThousandTwentyThreeNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_RealizedInvestmentGainsLossesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevolvingCreditFacilityMember" xlink:to="us-gaap_RevolvingCreditFacilityMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetwrixCorpMember" xlink:to="tslx_NetwrixCorpMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasic" xlink:to="us-gaap_EarningsPerShareBasic_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ManufacturingMember" xlink:to="tslx_ManufacturingMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" xlink:to="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AdviserMember" xlink:to="tslx_AdviserMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PaidInKindInterestIncome" xlink:to="tslx_PaidInKindInterestIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingencies" xlink:to="us-gaap_CommitmentsAndContingencies_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" xlink:to="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_IncomeStatementAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Investments" xlink:to="us-gaap_Investments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ArtisanBidcoIncMember" xlink:to="tslx_ArtisanBidcoIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" xlink:to="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputTypeAxis" xlink:to="us-gaap_MeasurementInputTypeAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeMember" xlink:to="srt_RangeMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_LossContingenciesLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RisksAssociatedWithConflictsOfInterestMember" xlink:to="tslx_RisksAssociatedWithConflictsOfInterestMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime" xlink:to="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsFairValueDisclosureNet" xlink:to="tslx_InvestmentsFairValueDisclosureNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:to="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentPeriodEndDate" xlink:to="dei_DocumentPeriodEndDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver" xlink:to="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIncomeDividend" xlink:to="us-gaap_InvestmentIncomeDividend_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareDiluted" xlink:to="us-gaap_EarningsPerShareDiluted_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BCTOAcePurchaserIncMember" xlink:to="tslx_BCTOAcePurchaserIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetUnrealizedGainsOnInvestments" xlink:to="tslx_NetUnrealizedGainsOnInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="us-gaap_DebtInstrumentNameDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CurrentMarketPricePerSharePercentage" xlink:to="tslx_CurrentMarketPricePerSharePercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OilGasAndConsumableFuelsMember" xlink:to="tslx_OilGasAndConsumableFuelsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock" xlink:to="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PdiTaHoldingsIncMember" xlink:to="tslx_PdiTaHoldingsIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SignificantAccountingPoliciesTable" xlink:to="tslx_SignificantAccountingPoliciesTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="us-gaap_RelatedPartyTransactionDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:to="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetExpenseForFederalExciseTax" xlink:to="tslx_NetExpenseForFederalExciseTax_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" xlink:to="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalCommonStock" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" xlink:to="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_MezzanineDebtInvestmentsMember" xlink:to="tslx_MezzanineDebtInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" xlink:to="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsNet" xlink:to="us-gaap_AssetsNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DividendDeclaredFromRealizedGainsPerShare" xlink:to="tslx_DividendDeclaredFromRealizedGainsPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockRepurchaseProgramPeriodInForce1" xlink:to="us-gaap_StockRepurchaseProgramPeriodInForce1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" xlink:to="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsOwnedEstimatedCostBasis" xlink:to="tslx_InvestmentsOwnedEstimatedCostBasis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressPostalZipCode" xlink:to="dei_EntityAddressPostalZipCode_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" xlink:to="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityInteractiveDataCurrent" xlink:to="dei_EntityInteractiveDataCurrent_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" xlink:to="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwentyTwentyThreeNotesMember" xlink:to="tslx_TwentyTwentyThreeNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputDiscountRateMember" xlink:to="us-gaap_MeasurementInputDiscountRateMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OverAllotmentOptionMember" xlink:to="us-gaap_OverAllotmentOptionMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_CreditFacilityDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" xlink:to="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_EquityAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_HeritageEnvironmentalServicesIncMember" xlink:to="tslx_HeritageEnvironmentalServicesIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_Project44IncMember" xlink:to="tslx_Project44IncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityIncorporationStateCountryCode" xlink:to="dei_EntityIncorporationStateCountryCode_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:to="us-gaap_CashAndCashEquivalentsPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_EarningsPerShareBasicAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:to="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PrimeRevenueIncMember" xlink:to="tslx_PrimeRevenueIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_StatementEquityComponentsAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LineOfCreditFacilityStatedMaturityDate" xlink:to="tslx_LineOfCreditFacilityStatedMaturityDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" xlink:to="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwentyTwentyTwoConvertibleNotesMember" xlink:to="tslx_TwentyTwentyTwoConvertibleNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LocalPhoneNumber" xlink:to="dei_LocalPhoneNumber_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SubsidiarySaleOfStockAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AgreementTerminationPeriodWithoutPenalty" xlink:to="tslx_AgreementTerminationPeriodWithoutPenalty_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:to="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DesignatedAsHedgingInstrumentMember" xlink:to="us-gaap_DesignatedAsHedgingInstrumentMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NonControlledAffiliatedInvestmentsMember" xlink:to="tslx_NonControlledAffiliatedInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_WestMember" xlink:to="tslx_WestMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RapidDataGmbhUnternehmensberatungMember" xlink:to="tslx_RapidDataGmbhUnternehmensberatungMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DelayedDrawRevolverEquityMember" xlink:to="tslx_DelayedDrawRevolverEquityMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LineOfCreditFacilityExtendedDate" xlink:to="tslx_LineOfCreditFacilityExtendedDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxAuthorityDomain" xlink:to="us-gaap_IncomeTaxAuthorityDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:to="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" xlink:to="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BctoBluebillBuyerIncMember" xlink:to="tslx_BctoBluebillBuyerIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AlaskaBidcoOyMember" xlink:to="tslx_AlaskaBidcoOyMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncreaseDecreaseInDistributableEarnings" xlink:to="tslx_IncreaseDecreaseInDistributableEarnings_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetExpense" xlink:to="tslx_NetExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentAdvisoryAgreementMember" xlink:to="tslx_InvestmentAdvisoryAgreementMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AmericanAchievementCorpMember" xlink:to="tslx_AmericanAchievementCorpMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapTenMember" xlink:to="tslx_InterestRateSwapTenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Dividends" xlink:to="us-gaap_Dividends_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SupplementalDividendMember" xlink:to="tslx_SupplementalDividendMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList" xlink:to="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionAxis" xlink:to="us-gaap_RelatedPartyTransactionAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityAverageOutstandingAmount" xlink:to="us-gaap_LineOfCreditFacilityAverageOutstandingAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" xlink:to="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsOfDividends" xlink:to="us-gaap_PaymentsOfDividends_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueInputsLevel3Member" xlink:to="us-gaap_FairValueInputsLevel3Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:to="us-gaap_TreasuryStockAcquiredAverageCostPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AccountingStandardsUpdate202206Member" xlink:to="tslx_AccountingStandardsUpdate202206Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:to="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock" xlink:to="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" xlink:to="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ElysianFincoLtdMember" xlink:to="tslx_ElysianFincoLtdMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpenseMember" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseMember" xlink:to="us-gaap_InterestExpenseMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestRateDerivativesAtFairValueNet" xlink:to="us-gaap_InterestRateDerivativesAtFairValueNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfInvestmentsAtFairValue" xlink:to="tslx_PercentageOfInvestmentsAtFairValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherGeneralAndAdministrativeExpense" xlink:to="us-gaap_OtherGeneralAndAdministrativeExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:to="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DividendsTextBlock" xlink:to="tslx_DividendsTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ChemicalsMember" xlink:to="tslx_ChemicalsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapTwelveMember" xlink:to="tslx_InterestRateSwapTwelveMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock" xlink:to="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CityAreaCode" xlink:to="dei_CityAreaCode_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapEightMember" xlink:to="tslx_InterestRateSwapEightMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LetterOfCreditMember" xlink:to="us-gaap_LetterOfCreditMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyFinancialHighlightsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" xlink:to="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AvalaraIncMember" xlink:to="tslx_AvalaraIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:to="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" xlink:to="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder" xlink:to="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:to="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_KangarooBidcoASMember" xlink:to="tslx_KangarooBidcoASMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" xlink:to="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:to="us-gaap_DerivativeBasisSpreadOnVariableRate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalPeriodFocus" xlink:to="dei_DocumentFiscalPeriodFocus_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentPolicyTextBlock" xlink:to="us-gaap_InvestmentPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_GB" xlink:to="country_GB_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueNetAssetLiability" xlink:to="us-gaap_FairValueNetAssetLiability_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NondesignatedMember" xlink:to="us-gaap_NondesignatedMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:to="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_TaxCreditCarryforwardLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_GainLossFormAdjustmentOfPaidInKindInterest" xlink:to="tslx_GainLossFormAdjustmentOfPaidInKindInterest_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FairValueOfAnEffectiveHedge" xlink:to="tslx_FairValueOfAnEffectiveHedge_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock" xlink:to="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsOfFinancingCosts" xlink:to="us-gaap_PaymentsOfFinancingCosts_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NondeductibleFederalExciseTaxPercentage" xlink:to="tslx_NondeductibleFederalExciseTaxPercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TransportationMember" xlink:to="tslx_TransportationMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_FI" xlink:to="country_FI_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PurchasesAndOriginationsOfInvestmentsNet" xlink:to="tslx_PurchasesAndOriginationsOfInvestmentsNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ValuationTechniqueCostOfInvestmentsMember" xlink:to="tslx_ValuationTechniqueCostOfInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolverAndPartnershipInterestMember" xlink:to="tslx_RevolverAndPartnershipInterestMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentDueDate" xlink:to="tslx_InvestmentDueDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ObligorGroupMember" xlink:to="srt_ObligorGroupMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" xlink:to="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LettersOfCreditOutstandingAmount" xlink:to="us-gaap_LettersOfCreditOutstandingAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RepaymentsOnInvestments" xlink:to="tslx_RepaymentsOnInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiscalPeriod" xlink:to="us-gaap_FiscalPeriod_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:to="srt_CumulativeEffectPeriodOfAdoptionDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UnrealizedLossOnInvestments" xlink:to="tslx_UnrealizedLossOnInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativesPolicyTextBlock" xlink:to="us-gaap_DerivativesPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ManagementFeeWaiverHurdle" xlink:to="tslx_ManagementFeeWaiverHurdle_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:to="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RealizedInvestmentGainsLosses" xlink:to="us-gaap_RealizedInvestmentGainsLosses_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:to="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_GalileoParentincMember" xlink:to="tslx_GalileoParentincMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCommonStockSharesOutstanding" xlink:to="dei_EntityCommonStockSharesOutstanding_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LeverageWaiverMember" xlink:to="tslx_LeverageWaiverMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PartnershipInterestOwnershipPercentage" xlink:to="tslx_PartnershipInterestOwnershipPercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TradingSecuritiesDebt" xlink:to="us-gaap_TradingSecuritiesDebt_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EdgeBidcoBVMember" xlink:to="tslx_EdgeBidcoBVMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfDebtTableTextBlock" xlink:to="us-gaap_ScheduleOfDebtTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProfessionalFees" xlink:to="us-gaap_ProfessionalFees_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentOwnedBalanceShares" xlink:to="us-gaap_InvestmentOwnedBalanceShares_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockValue" xlink:to="us-gaap_TreasuryStockValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ControlledAffiliatedInvestmentsMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SellingGeneralAndAdministrativeExpense" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsDomain" xlink:to="us-gaap_DividendsDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalYearFocus" xlink:to="dei_DocumentFiscalYearFocus_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SwapSettlement" xlink:to="tslx_SwapSettlement_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AsgIiLlcMember" xlink:to="tslx_AsgIiLlcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayableFairValueDisclosure" xlink:to="us-gaap_NotesPayableFairValueDisclosure_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BtrsHoldingIncMember" xlink:to="tslx_BtrsHoldingIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TaxCostOfInvestments" xlink:to="tslx_TaxCostOfInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList" xlink:to="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" xlink:to="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ExtinguishmentOfDebtAmount" xlink:to="us-gaap_ExtinguishmentOfDebtAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_HippoXpaBidcoAbMember" xlink:to="tslx_HippoXpaBidcoAbMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EMSLinqIncMember" xlink:to="tslx_EMSLinqIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SecondLienDebtInvestmentsMember" xlink:to="tslx_SecondLienDebtInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncentiveFeesOnNetInvestmentIncome" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncome_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_SecurityExchangeName" xlink:to="dei_SecurityExchangeName_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:to="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DomesticCountryMember" xlink:to="us-gaap_DomesticCountryMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapTwoMember" xlink:to="tslx_InterestRateSwapTwoMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DistributedEarnings" xlink:to="us-gaap_DistributedEarnings_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesIssued" xlink:to="us-gaap_PreferredStockSharesIssued_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesAuthorized" xlink:to="us-gaap_PreferredStockSharesAuthorized_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PerShareMarketValueAtEndPeriod" xlink:to="tslx_PerShareMarketValueAtEndPeriod_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolvingCreditFacilityMaturityOnApril242029Member" xlink:to="tslx_RevolvingCreditFacilityMaturityOnApril242029Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentsAtFairValueTextBlock" xlink:to="tslx_InvestmentsAtFairValueTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayable" xlink:to="us-gaap_NotesPayable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquitySecuritiesByIndustryAxis" xlink:to="us-gaap_EquitySecuritiesByIndustryAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:to="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_HedgingDesignationDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockSharesAcquired" xlink:to="us-gaap_TreasuryStockSharesAcquired_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_FinancialInstrumentAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityCommitmentFeeAmount" xlink:to="us-gaap_LineOfCreditFacilityCommitmentFeeAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityEmergingGrowthCompany" xlink:to="dei_EntityEmergingGrowthCompany_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PurchaseCommitmentToFundInvestment" xlink:to="tslx_PurchaseCommitmentToFundInvestment_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MarketApproachValuationTechniqueMember" xlink:to="us-gaap_MarketApproachValuationTechniqueMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" xlink:to="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherBookTaxDifferences" xlink:to="tslx_OtherBookTaxDifferences_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="us-gaap_TypeOfAdoptionMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OfficeProductsMember" xlink:to="tslx_OfficeProductsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:to="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CommunicationsMember" xlink:to="tslx_CommunicationsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" xlink:to="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeGainLossOnDerivativeNet" xlink:to="us-gaap_DerivativeGainLossOnDerivativeNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_VariableRateDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:to="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFileNumber" xlink:to="dei_EntityFileNumber_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ApteanIncMember" xlink:to="tslx_ApteanIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityExpirationDate1" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" xlink:to="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PledgedStatusDomain" xlink:to="us-gaap_PledgedStatusDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredTaxAssetsGross" xlink:to="us-gaap_DeferredTaxAssetsGross_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherLiabilities" xlink:to="us-gaap_OtherLiabilities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ExtraHopNetworksIncMember" xlink:to="tslx_ExtraHopNetworksIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EquityAndOtherInvestmentsMember" xlink:to="tslx_EquityAndOtherInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" xlink:to="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AdditionalAggregatePrincipalAmount" xlink:to="tslx_AdditionalAggregatePrincipalAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AxonifyIncMember" xlink:to="tslx_AxonifyIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_DE" xlink:to="country_DE_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PassportLabsIncMember" xlink:to="tslx_PassportLabsIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:to="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock" xlink:to="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingExpenses_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DividendsPolicyTextBlock" xlink:to="tslx_DividendsPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapSevenMember" xlink:to="tslx_InterestRateSwapSevenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressAddressLine2" xlink:to="dei_EntityAddressAddressLine2_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValue" xlink:to="us-gaap_PreferredStockValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntitySmallBusiness" xlink:to="dei_EntitySmallBusiness_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_FirstLienDebtInvestmentsMember" xlink:to="tslx_FirstLienDebtInvestmentsMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityShellCompany" xlink:to="dei_EntityShellCompany_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsAbstract" xlink:to="us-gaap_DividendsAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:to="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GainLossOnSaleOfDerivatives" xlink:to="us-gaap_GainLossOnSaleOfDerivatives_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentAcquisitionDate" xlink:to="us-gaap_InvestmentAcquisitionDate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareTextBlock" xlink:to="us-gaap_EarningsPerShareTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherIncomePolicyTextBlock" xlink:to="tslx_OtherIncomePolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityAddressAddressLine1" xlink:to="dei_EntityAddressAddressLine1_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EquityAndOtherInvestments" xlink:to="tslx_EquityAndOtherInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ErlingLuxBidcoSarlMember" xlink:to="tslx_ErlingLuxBidcoSarlMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeApproachValuationTechniqueMember" xlink:to="us-gaap_IncomeApproachValuationTechniqueMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IssuanceOfCommonStockNetOfOfferingCosts" xlink:to="tslx_IssuanceOfCommonStockNetOfOfferingCosts_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedCash" xlink:to="us-gaap_RestrictedCash_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BenNevisMidcoLimitedMember" xlink:to="tslx_BenNevisMidcoLimitedMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:to="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BayshoreIntermediate2LPMember" xlink:to="tslx_BayshoreIntermediate2LPMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventTypeDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock" xlink:to="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncentiveFeeExpense" xlink:to="us-gaap_IncentiveFeeExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfDebtDiscountPremium" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapElevenMember" xlink:to="tslx_InterestRateSwapElevenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CrewlineBuyerIncMember" xlink:to="tslx_CrewlineBuyerIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsDeclaredTableTextBlock" xlink:to="us-gaap_DividendsDeclaredTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_ProfitLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" xlink:to="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueInputsLevel2Member" xlink:to="us-gaap_FairValueInputsLevel2Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PercentageOfIncentiveFeeRate" xlink:to="tslx_PercentageOfIncentiveFeeRate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsPayableTable" xlink:to="us-gaap_DividendsPayableTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DelayedDrawEquityMember" xlink:to="tslx_DelayedDrawEquityMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentCarryingAmount" xlink:to="us-gaap_DebtInstrumentCarryingAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:to="us-gaap_TreasuryStockValueAcquiredCostMethod_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset" xlink:to="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_Security12bTitle" xlink:to="dei_Security12bTitle_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ManagementFeeExpense" xlink:to="us-gaap_ManagementFeeExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="us-gaap_EquitySecuritiesIndustryMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DeferredOrganizationCosts" xlink:to="tslx_DeferredOrganizationCosts_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LegislationAllowsToIncurAdditionalLeverageMember" xlink:to="tslx_LegislationAllowsToIncurAdditionalLeverageMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentySixNotesMember" xlink:to="tslx_TwoThousandTwentySixNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="us-gaap_InvestmentTypeCategorizationMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" xlink:to="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ArrowbuyerIncMember" xlink:to="tslx_ArrowbuyerIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockCommonMember" xlink:to="us-gaap_TreasuryStockCommonMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfFinancingCosts" xlink:to="us-gaap_AmortizationOfFinancingCosts_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestRateSwapMember" xlink:to="us-gaap_InterestRateSwapMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherIncomeForTaxPurposesNotBook" xlink:to="tslx_OtherIncomeForTaxPurposesNotBook_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LineOfCredit" xlink:to="us-gaap_LineOfCredit_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:to="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherExpensesNotCurrentlyDeductible" xlink:to="tslx_OtherExpensesNotCurrentlyDeductible_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwentyTwentyNineNotesMember" xlink:to="tslx_TwentyTwentyNineNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativesOffsettingFairValueAmountsPolicy" xlink:to="us-gaap_DerivativesOffsettingFairValueAmountsPolicy_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TaxCreditCarryforwardTable" xlink:to="us-gaap_TaxCreditCarryforwardTable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CordanceOperationsLlcMember" xlink:to="tslx_CordanceOperationsLlcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UnrealizedGainsLossesOnIncomeTaxProvision" xlink:to="tslx_UnrealizedGainsLossesOnIncomeTaxProvision_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:to="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EducationMember" xlink:to="tslx_EducationMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebt" xlink:to="us-gaap_InterestExpenseDebt_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" xlink:to="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UnfundedLoanCommitmentMember" xlink:to="us-gaap_UnfundedLoanCommitmentMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapFiveMember" xlink:to="tslx_InterestRateSwapFiveMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ReliaQuestHoldingsLLCMember" xlink:to="tslx_ReliaQuestHoldingsLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_MarcuraEquitiesLtdMember" xlink:to="tslx_MarcuraEquitiesLtdMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AssetCoveragePercentage" xlink:to="tslx_AssetCoveragePercentage_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LeantaasHoldingsIncMember" xlink:to="tslx_LeantaasHoldingsIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwoThousandTwentyEightNotesMember" xlink:to="tslx_TwoThousandTwentyEightNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_NO" xlink:to="country_NO_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_MidwestMember" xlink:to="tslx_MidwestMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends" xlink:to="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EDBParentLLCMember" xlink:to="tslx_EDBParentLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncreaseDecreaseInInterestReceivablePaidInKind" xlink:to="tslx_IncreaseDecreaseInInterestReceivablePaidInKind_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIdentifierAxis" xlink:to="us-gaap_InvestmentIdentifierAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapNineMember" xlink:to="tslx_InterestRateSwapNineMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherCommitment" xlink:to="us-gaap_OtherCommitment_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_IncomeStatementLocationDomain_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:to="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TotalReturnBasedOnNetAssetValue" xlink:to="tslx_TotalReturnBasedOnNetAssetValue_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentInterestRate" xlink:to="us-gaap_InvestmentInterestRate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentQuarterlyReport" xlink:to="dei_DocumentQuarterlyReport_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_AdministrationAgreementMember" xlink:to="tslx_AdministrationAgreementMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" xlink:to="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrepaidExpenseAndOtherAssets" xlink:to="us-gaap_PrepaidExpenseAndOtherAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SkylarkUkDebtcoLimitedMember" xlink:to="tslx_SkylarkUkDebtcoLimitedMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetAssetValuePerShare" xlink:to="us-gaap_NetAssetValuePerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CostModelMember" xlink:to="tslx_CostModelMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DerivativeNotionalAmount" xlink:to="us-gaap_DerivativeNotionalAmount_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock" xlink:to="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" xlink:to="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_BlackScholesModelMember" xlink:to="tslx_BlackScholesModelMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_MarketingServicesMember" xlink:to="tslx_MarketingServicesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PledgedStatusAxis" xlink:to="us-gaap_PledgedStatusAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFilerCategory" xlink:to="dei_EntityFilerCategory_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:to="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_UnrealizedGainOnInvestments" xlink:to="tslx_UnrealizedGainOnInvestments_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" xlink:to="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" xlink:to="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DelayedDrawAndRevolverMember" xlink:to="tslx_DelayedDrawAndRevolverMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LongTermCapitalGains" xlink:to="tslx_LongTermCapitalGains_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForHedgeInvestingActivities" xlink:to="us-gaap_PaymentsForHedgeInvestingActivities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_NonoperatingIncomeExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_EmploymentHeroHoldingsPtyLtdMember" xlink:to="tslx_EmploymentHeroHoldingsPtyLtdMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" xlink:to="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_LaramieEnergyLLCMember" xlink:to="tslx_LaramieEnergyLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestReceivable" xlink:to="us-gaap_InterestReceivable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember" xlink:to="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DyeDurhamCorpMember" xlink:to="tslx_DyeDurhamCorpMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendPayableDateToBePaidDayMonthAndYear" xlink:to="us-gaap_DividendPayableDateToBePaidDayMonthAndYear_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SlBuyerCorpMember" xlink:to="tslx_SlBuyerCorpMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_CoupaHoldingsLLCMember" xlink:to="tslx_CoupaHoldingsLLCMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ThreeMonthLiborMember" xlink:to="tslx_ThreeMonthLiborMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InvestmentCompanyRepurchaseOfDebtPerShare" xlink:to="tslx_InvestmentCompanyRepurchaseOfDebtPerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:to="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_NonoperatingIncomeExpenseAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpense" xlink:to="us-gaap_InterestExpense_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:to="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_SignificantAccountingPoliciesLineItems_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_KyribaCorpMember" xlink:to="tslx_KyribaCorpMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DividendsPayableNature" xlink:to="us-gaap_DividendsPayableNature_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock" xlink:to="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DelayedDrawAndMembershipInterestMember" xlink:to="tslx_DelayedDrawAndMembershipInterestMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputComparabilityAdjustmentMember" xlink:to="us-gaap_MeasurementInputComparabilityAdjustmentMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" xlink:to="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementOfFinancialPositionAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwentyTwentyFourNotesMember" xlink:to="tslx_TwentyTwentyFourNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_WranglerTopcoLlcMember" xlink:to="tslx_WranglerTopcoLlcMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_PingIdentityCorporationMember" xlink:to="tslx_PingIdentityCorporationMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesIssuedPricePerShare" xlink:to="us-gaap_SharesIssuedPricePerShare_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_HirevueIncMember" xlink:to="tslx_HirevueIncMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:to="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_UseOfEstimates" xlink:to="us-gaap_UseOfEstimates_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_InterestRateSwapThirteenMember" xlink:to="tslx_InterestRateSwapThirteenMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_TwentyTwentySixNotesMember" xlink:to="tslx_TwentyTwentySixNotesMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureTextBlock" xlink:to="us-gaap_IncomeTaxDisclosureTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" xlink:to="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ValuationTechniqueAxis" xlink:to="us-gaap_ValuationTechniqueAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueDisclosuresAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CurrentIncomeTaxExpenseBenefit" xlink:to="us-gaap_CurrentIncomeTaxExpenseBenefit_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:to="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationAxis_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_ProceedsFromInvestmentsNet" xlink:to="tslx_ProceedsFromInvestmentsNet_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromUnsecuredNotesPayable" xlink:to="us-gaap_ProceedsFromUnsecuredNotesPayable_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tslx_OtherMember" xlink:to="tslx_OtherMember_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AlternativeInvestment" xlink:to="us-gaap_AlternativeInvestment_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_IncomeTaxDisclosureAbstract_lbl"/>
          <link:labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetPledgedAsCollateralMember" xlink:to="us-gaap_AssetPledgedAsCollateralMember_lbl"/>
        </link:labelLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DocumentDocumentAndEntityInformation" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CoverAbstract" xlink:label="dei_CoverAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentType" xlink:label="dei_DocumentType"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_TradingSymbol" xlink:label="dei_TradingSymbol"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentQuarterlyReport" xlink:label="dei_DocumentQuarterlyReport"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_DocumentTransitionReport" xlink:label="dei_DocumentTransitionReport"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityInteractiveDataCurrent" xlink:label="dei_EntityInteractiveDataCurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityShellCompany" xlink:label="dei_EntityShellCompany"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntitySmallBusiness" xlink:label="dei_EntitySmallBusiness"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityFileNumber" xlink:label="dei_EntityFileNumber"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityTaxIdentificationNumber" xlink:label="dei_EntityTaxIdentificationNumber"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityIncorporationStateCountryCode" xlink:label="dei_EntityIncorporationStateCountryCode"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine1" xlink:label="dei_EntityAddressAddressLine1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressAddressLine2" xlink:label="dei_EntityAddressAddressLine2"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressCityOrTown" xlink:label="dei_EntityAddressCityOrTown"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressStateOrProvince" xlink:label="dei_EntityAddressStateOrProvince"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityAddressPostalZipCode" xlink:label="dei_EntityAddressPostalZipCode"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_CityAreaCode" xlink:label="dei_CityAreaCode"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_LocalPhoneNumber" xlink:label="dei_LocalPhoneNumber"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_Security12bTitle" xlink:label="dei_Security12bTitle"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2023/dei-2023.xsd#dei_SecurityExchangeName" xlink:label="dei_SecurityExchangeName"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentType" order="49.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_AmendmentFlag" order="50.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentPeriodEndDate" order="51.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentFiscalYearFocus" order="52.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentFiscalPeriodFocus" order="53.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_TradingSymbol" order="54.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityRegistrantName" order="55.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityCentralIndexKey" order="56.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_CurrentFiscalYearEndDate" order="57.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentQuarterlyReport" order="58.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_DocumentTransitionReport" order="59.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityCurrentReportingStatus" order="60.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityInteractiveDataCurrent" order="61.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityFilerCategory" order="62.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityShellCompany" order="63.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntitySmallBusiness" order="64.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityEmergingGrowthCompany" order="65.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityFileNumber" order="66.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityTaxIdentificationNumber" order="67.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityIncorporationStateCountryCode" order="68.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressAddressLine1" order="69.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressAddressLine2" order="70.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressCityOrTown" order="71.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressStateOrProvince" order="72.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityAddressPostalZipCode" order="73.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_CityAreaCode" order="74.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_LocalPhoneNumber" order="75.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_EntityCommonStockSharesOutstanding" order="76.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_Security12bTitle" order="77.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="dei_CoverAbstract" xlink:to="dei_SecurityExchangeName" order="78.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnaudited" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAbstract" xlink:label="us-gaap_LiabilitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeePayable" xlink:label="us-gaap_ManagementFeePayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestReceivable" xlink:label="us-gaap_InterestReceivable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssets" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherPayablesToAffiliate" xlink:label="tslx_OtherPayablesToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities" xlink:label="us-gaap_OtherLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsNet" xlink:label="us-gaap_AssetsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetAssetValuePerShare" xlink:label="us-gaap_NetAssetValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_InvestmentOwnedAtFairValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_LongTermDebt" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_PreferredStockValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentTypeAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AssetsAbstract" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_ManagementFeePayable" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_CommonStockValue" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAbstract" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_InterestReceivable" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommitmentsAndContingencies" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_PrepaidExpenseAndOtherAssets" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_TreasuryStockValue" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquityAbstract" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_Assets" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="tslx_OtherPayablesToAffiliate" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_OtherLiabilities" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_AssetsNet" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedTotalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetAssetValuePerShare" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_Liabilities" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtCost" xlink:label="us-gaap_InvestmentOwnedAtCost"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash" xlink:label="us-gaap_RestrictedCash"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonShares" xlink:label="us-gaap_TreasuryStockCommonShares"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentTypeAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtCost" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_RestrictedCash" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledAffiliatedInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DeferredFinanceCostsNet" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesAuthorized" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesIssued" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesOutstanding" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesAuthorized" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesIssued" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesOutstanding" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockCommonShares" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfOperationsUnaudited" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnInvestments" xlink:label="us-gaap_UnrealizedGainLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLosses" xlink:label="us-gaap_RealizedInvestmentGainsLosses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeInterest" xlink:label="us-gaap_InvestmentIncomeInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeeExpense" xlink:label="us-gaap_ManagementFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfDerivatives" xlink:label="us-gaap_GainLossOnSaleOfDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaidInKindInterestIncome" xlink:label="tslx_PaidInKindInterestIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncome" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeDividend" xlink:label="us-gaap_InvestmentIncomeDividend"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainsLossesOnIncomeTaxProvision" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGains" xlink:label="tslx_IncentiveFeesOnNetCapitalGains"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncome" xlink:label="us-gaap_OtherNonoperatingIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfessionalFees" xlink:label="us-gaap_ProfessionalFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet" xlink:label="us-gaap_InvestmentIncomeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpenseDirectorsFees" xlink:label="us-gaap_NoninterestExpenseDirectorsFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherGeneralAndAdministrativeExpense" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementAndIncentiveFeeWaived" xlink:label="tslx_ManagementAndIncentiveFeeWaived"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpense" xlink:label="tslx_NetExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_UnrealizedGainLossOnInvestments" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_InterestExpense" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_RealizedInvestmentGainsLosses" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentTypeAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NonoperatingIncomeExpenseAbstract" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:to="tslx_UnRealizedInvestmentGainsLossesAbstract" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_InvestmentIncomeInterest" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_ManagementFeeExpense" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_GainLossOnSaleOfDerivatives" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_OperatingExpensesAbstract" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:to="us-gaap_RealizedInvestmentGainsLossesAbstract" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledAffiliatedInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="tslx_PaidInKindInterestIncome" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncome" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossRealized" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_InvestmentIncomeDividend" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="tslx_UnrealizedGainsLossesOnIncomeTaxProvision" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_IncentiveFeesOnNetCapitalGains" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_OtherNonoperatingIncome" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_ProfessionalFees" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentIncomeNet" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_NonoperatingIncomeExpense" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_NoninterestExpenseDirectorsFees" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OtherGeneralAndAdministrativeExpense" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpenses" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ProfitLoss" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_ManagementAndIncentiveFeeWaived" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_EarningsPerShareBasic" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_NetExpense" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_EarningsPerShareDiluted" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnaudited" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentDueDate" xlink:label="tslx_InvestmentDueDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAcquisitionDate" xlink:label="us-gaap_InvestmentAcquisitionDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentBasisSpreadVariableRate" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentInterestRate" xlink:label="us-gaap_InvestmentInterestRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentInterestRatePaidInKind" xlink:label="us-gaap_InvestmentInterestRatePaidInKind"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtCost" xlink:label="us-gaap_InvestmentOwnedAtCost"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateDerivativesAtFairValueNet" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PartnershipInterestOwnershipPercentage" xlink:label="tslx_PartnershipInterestOwnershipPercentage"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentDueDate" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentAcquisitionDate" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentBasisSpreadVariableRate" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentInterestRate" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentInterestRatePaidInKind" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtCost" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtFairValue" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedPercentOfNetAssets" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeBasisSpreadOnVariableRate" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeMaturityDates" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InterestRateDerivativesAtFairValueNet" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeGainLossOnDerivativeNet" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeFairValueOfDerivativeNet" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" order="17" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PartnershipInterestOwnershipPercentage" order="18" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DomesticCountryMember" xlink:label="us-gaap_DomesticCountryMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentDueDate" xlink:label="tslx_InvestmentDueDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateDerivativesAtFairValueNet" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNonQualifyingAssets" xlink:label="tslx_PercentageOfNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsOwnedEstimatedCostBasis" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainOnInvestments" xlink:label="tslx_UnrealizedGainOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedLossOnInvestments" xlink:label="tslx_UnrealizedLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PartnershipInterestOwnershipPercentage" xlink:label="tslx_PartnershipInterestOwnershipPercentage"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxAuthorityDomain" xlink:to="us-gaap_DomesticCountryMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_NondesignatedMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_HedgingDesignationAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentDueDate" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_IncomeTaxAuthorityAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InterestRateDerivativesAtFairValueNet" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PercentageOfNonQualifyingAssets" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsOwnedEstimatedCostBasis" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UnrealizedGainOnInvestments" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UnrealizedLossOnInvestments" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PartnershipInterestOwnershipPercentage" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnaudited" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue_5"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtFairValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtFairValue_5" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParenthetical" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfStockholdersEquityAbstract" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonMember" xlink:label="us-gaap_TreasuryStockCommonMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet" xlink:label="us-gaap_InvestmentIncomeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Dividends" xlink:label="us-gaap_Dividends"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxReclassificationOfStockholdersEquity" xlink:label="tslx_TaxReclassificationOfStockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity_13"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding_14"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="us-gaap_StatementTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_CommonStockMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:to="srt_CumulativeEffectPeriodOfAdoptionDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquity" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_TreasuryStockCommonMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesOutstanding" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentIncomeNet" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_Dividends" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_TaxReclassificationOfStockholdersEquity" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquity_13" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesOutstanding_14" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestPaidNet" xlink:label="us-gaap_InterestPaidNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnInvestments" xlink:label="us-gaap_UnrealizedGainLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromShortTermDebt" xlink:label="us-gaap_ProceedsFromShortTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInInterestReceivablePaidInKind" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxesPaid" xlink:label="us-gaap_IncomeTaxesPaid"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfShortTermDebt" xlink:label="us-gaap_RepaymentsOfShortTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredDuringThePeriod" xlink:label="tslx_DividendsDeclaredDuringThePeriod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfFinancingCosts" xlink:label="us-gaap_PaymentsOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLosses" xlink:label="us-gaap_RealizedInvestmentGainsLosses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_4"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfDividends" xlink:label="us-gaap_PaymentsOfDividends"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfDerivatives" xlink:label="us-gaap_GainLossOnSaleOfDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PurchasesAndOriginationsOfInvestmentsNet" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ProceedsFromInvestmentsNet" xlink:label="tslx_ProceedsFromInvestmentsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RepaymentsOnInvestments" xlink:label="tslx_RepaymentsOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_GainLossFormAdjustmentOfPaidInKindInterest" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_InterestPaidNet" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_UnrealizedGainLossOnInvestments" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ProfitLoss" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromShortTermDebt" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStockDividendReinvestmentPlan" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="tslx_IncreaseDecreaseInInterestReceivablePaidInKind" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_IncomeTaxesPaid" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_RepaymentsOfShortTermDebt" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="tslx_DividendsDeclaredDuringThePeriod" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsOfFinancingCosts" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_RealizedInvestmentGainsLosses" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_4" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_PaymentsOfDividends" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_GainLossOnSaleOfDerivatives" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AmortizationOfFinancingCosts" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="tslx_PurchasesAndOriginationsOfInvestmentsNet" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="tslx_ProceedsFromInvestmentsNet" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="tslx_RepaymentsOnInvestments" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="tslx_GainLossFormAdjustmentOfPaidInKindInterest" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://xbrl.sec.gov/cef/role/N2" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/cef/2023/cef-2023.xsd#cef_AllRisksMember" xlink:label="cef_AllRisksMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RisksAssociatedWithChangesInInterestRatesMember" xlink:label="tslx_RisksAssociatedWithChangesInInterestRatesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RisksAssociatedWithConflictsOfInterestMember" xlink:label="tslx_RisksAssociatedWithConflictsOfInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyThreeNotesMember" xlink:label="tslx_TwentyTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" xlink:label="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyFourNotesMember" xlink:label="tslx_TwentyTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LegislationAllowsToIncurAdditionalLeverageMember" xlink:label="tslx_LegislationAllowsToIncurAdditionalLeverageMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentySixNotesMember" xlink:label="tslx_TwentyTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" xlink:label="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyEightNotesMember" xlink:label="tslx_TwentyTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" xlink:label="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyNineNotesMember" xlink:label="tslx_TwentyTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" xlink:label="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" xlink:label="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_RisksAssociatedWithChangesInInterestRatesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyTwoConvertibleNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_RisksAssociatedWithConflictsOfInterestMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyThreeNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyFourNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_LegislationAllowsToIncurAdditionalLeverageMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentySixNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyEightNotesMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyNineNotesMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="cef_AllRisksMember" xlink:to="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureOrganizationAndBasisOfPresentation" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:label="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsAbstract" xlink:to="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPolicies" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SignificantAccountingPoliciesTextBlock" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_SignificantAccountingPoliciesTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactions" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsAbstract" xlink:label="us-gaap_RelatedPartyTransactionsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsDisclosureTextBlock" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionsAbstract" xlink:to="us-gaap_RelatedPartyTransactionsDisclosureTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValue" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsAtFairValueTextBlock" xlink:label="tslx_InvestmentsAtFairValueTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="tslx_InvestmentsAtFairValueTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivatives" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresTextBlock" xlink:label="us-gaap_FairValueDisclosuresTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueDisclosuresTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebt" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureTextBlock" xlink:label="us-gaap_DebtDisclosureTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtDisclosureTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingencies" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssets" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract" xlink:label="us-gaap_EquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityNoteDisclosureTextBlock" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_StockholdersEquityNoteDisclosureTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShare" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="us-gaap_EarningsPerShareAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareTextBlock" xlink:label="us-gaap_EarningsPerShareTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareAbstract" xlink:to="us-gaap_EarningsPerShareTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividends" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAbstract" xlink:label="us-gaap_DividendsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsTextBlock" xlink:label="tslx_DividendsTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsAbstract" xlink:to="tslx_DividendsTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxes" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureTextBlock" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_IncomeTaxDisclosureTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFinancialHighlights" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyFinancialHighlightsTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSubsequentEvents" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventsAbstract" xlink:label="us-gaap_SubsequentEventsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventsTextBlock" xlink:label="us-gaap_SubsequentEventsTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SubsequentEventsAbstract" xlink:to="us-gaap_SubsequentEventsTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesPolicies" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BasisOfAccountingPolicyPolicyTextBlock" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FiscalPeriod" xlink:label="us-gaap_FiscalPeriod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UseOfEstimates" xlink:label="us-gaap_UseOfEstimates"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsPolicyTextBlock" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentPolicyTextBlock" xlink:label="us-gaap_InvestmentPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesPolicyTextBlock" xlink:label="us-gaap_DerivativesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock" xlink:label="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:label="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityOfferingExpensesPolicyTextBlock" xlink:label="tslx_EquityOfferingExpensesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtPolicyTextBlock" xlink:label="us-gaap_DebtPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock" xlink:label="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherIncomePolicyTextBlock" xlink:label="tslx_OtherIncomePolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerSharePolicyTextBlock" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" xlink:label="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock" xlink:label="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsPolicyTextBlock" xlink:label="tslx_DividendsPolicyTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativesOffsettingFairValueAmountsPolicy" xlink:label="us-gaap_DerivativesOffsettingFairValueAmountsPolicy"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_BasisOfAccountingPolicyPolicyTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_FiscalPeriod" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_UseOfEstimates" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_CashAndCashEquivalentsPolicyTextBlock" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_InvestmentPolicyTextBlock" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_DerivativesPolicyTextBlock" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_EquityOfferingExpensesPolicyTextBlock" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_DebtPolicyTextBlock" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_OtherIncomePolicyTextBlock" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_EarningsPerSharePolicyTextBlock" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_DividendsPolicyTextBlock" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="us-gaap_DerivativesOffsettingFairValueAmountsPolicy" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock" xlink:label="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" xlink:label="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfDerivativeInstrumentsTextBlock" xlink:label="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="us-gaap_ScheduleOfDerivativeInstrumentsTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock" xlink:label="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTextBlock" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisGainLossIncludedInEarningsTextBlock" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_ScheduleOfCarryingValuesAndEstimatedFairValuesOfDebtInstrumentsTableTextBlock" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock" xlink:label="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" xlink:label="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfDebtTableTextBlock" xlink:label="us-gaap_ScheduleOfDebtTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_ScheduleOfDebtTableTextBlock" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" xlink:label="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract" xlink:label="us-gaap_EquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" xlink:label="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityAbstract" xlink:to="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="us-gaap_EarningsPerShareAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareAbstract" xlink:to="us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAbstract" xlink:label="us-gaap_DividendsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDeclaredTableTextBlock" xlink:label="us-gaap_DividendsDeclaredTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsAbstract" xlink:to="us-gaap_DividendsDeclaredTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock" xlink:label="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock" xlink:label="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock" xlink:label="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFinancialHighlightsTables" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyFinancialHighlightsTableTextBlock" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SignificantAccountingPoliciesTable" xlink:label="tslx_SignificantAccountingPoliciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AccountingStandardsUpdate202206Member" xlink:label="tslx_AccountingStandardsUpdate202206Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SignificantAccountingPoliciesLineItems" xlink:label="tslx_SignificantAccountingPoliciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NondeductibleFederalExciseTaxPercentage" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AccountingPoliciesAbstract" xlink:to="tslx_SignificantAccountingPoliciesTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesTable" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="tslx_AccountingStandardsUpdate202206Member" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_TypeOfAdoptionMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesTable" xlink:to="tslx_SignificantAccountingPoliciesLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_NondeductibleFederalExciseTaxPercentage" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsAbstract" xlink:label="us-gaap_RelatedPartyTransactionsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="us-gaap_RelatedPartyTransactionLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AgreementTerminationPeriodWithoutPenalty" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="srt_ScenarioUnspecifiedDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioForecastMember" xlink:label="srt_ScenarioForecastMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdviserMember" xlink:label="tslx_AdviserMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementScenarioAxis" xlink:label="srt_StatementScenarioAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="us-gaap_RelatedPartyTransactionDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdministrationAgreementMember" xlink:label="tslx_AdministrationAgreementMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember" xlink:label="us-gaap_RelatedPartyMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="us-gaap_RelatedPartyTransactionAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LeverageWaiverMember" xlink:label="tslx_LeverageWaiverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentAdvisoryAgreementMember" xlink:label="tslx_InvestmentAdvisoryAgreementMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeeExpense" xlink:label="us-gaap_ManagementFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementFeeWaiverHurdle" xlink:label="tslx_ManagementFeeWaiverHurdle"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfIncentiveFeeRate" xlink:label="tslx_PercentageOfIncentiveFeeRate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Investments" xlink:label="us-gaap_Investments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncentiveFeeExpense" xlink:label="us-gaap_IncentiveFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesRealizedAndPayableToAdvisor" xlink:label="tslx_IncentiveFeesRealizedAndPayableToAdvisor"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncome" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionsAbstract" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_AgreementTerminationPeriodWithoutPenalty" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="srt_ScenarioForecastMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="tslx_AdviserMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_ScenarioUnspecifiedDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="tslx_AdministrationAgreementMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:to="us-gaap_RelatedPartyMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionAxis" xlink:to="us-gaap_RelatedPartyTransactionDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedPartyTransactionAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="tslx_LeverageWaiverMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="tslx_InvestmentAdvisoryAgreementMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="srt_StatementScenarioAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_ManagementFeeExpense" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusAxis" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_ManagementFeeWaiverHurdle" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_SubsequentEventTypeAxis" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="srt_RangeAxis" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_IncomeStatementLocationAxis" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedPartyTransactionLineItems" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" order="17" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" order="18" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfIncentiveFeeRate" order="19" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" order="20" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_Investments" order="21" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_IncentiveFeeExpense" order="22" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_IncentiveFeesRealizedAndPayableToAdvisor" order="23" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncome" order="24" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" order="25" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfInvestmentsAtFairValueDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestmentsMember" xlink:label="tslx_StructuredCreditInvestmentsMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_FinancialInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_FirstLienDebtInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_SecondLienDebtInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_MezzanineDebtInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_EquityAndOtherInvestmentsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_StructuredCreditInvestmentsMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfIndustryCompositionOfInvestmentsAtFairValueDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesByIndustryAxis" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesIndustryMember" xlink:label="us-gaap_EquitySecuritiesIndustryMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AutomotiveMember" xlink:label="tslx_AutomotiveMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BusinessServicesMember" xlink:label="tslx_BusinessServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ChemicalsMember" xlink:label="tslx_ChemicalsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CommunicationsMember" xlink:label="tslx_CommunicationsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EducationMember" xlink:label="tslx_EducationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialServicesSectorMember" xlink:label="us-gaap_FinancialServicesSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HealthcareSectorMember" xlink:label="us-gaap_HealthcareSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HotelGamingAndLeisureMember" xlink:label="tslx_HotelGamingAndLeisureMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HumanResourceSupportServicesMember" xlink:label="tslx_HumanResourceSupportServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InsuranceMember" xlink:label="tslx_InsuranceMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InternetServicesMember" xlink:label="tslx_InternetServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManufacturingMember" xlink:label="tslx_ManufacturingMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MarketingServicesMember" xlink:label="tslx_MarketingServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OfficeProductsMember" xlink:label="tslx_OfficeProductsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OilGasAndConsumableFuelsMember" xlink:label="tslx_OilGasAndConsumableFuelsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherMember" xlink:label="tslx_OtherMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RetailAndConsumerProductsMember" xlink:label="tslx_RetailAndConsumerProductsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TransportationMember" xlink:label="tslx_TransportationMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_EquitySecuritiesByIndustryAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="tslx_PercentageOfInvestmentsAtFairValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesByIndustryAxis" xlink:to="us-gaap_EquitySecuritiesIndustryMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_AutomotiveMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_BusinessServicesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_ChemicalsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_CommunicationsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_EducationMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="us-gaap_FinancialServicesSectorMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="us-gaap_HealthcareSectorMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_HotelGamingAndLeisureMember" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_HumanResourceSupportServicesMember" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_InsuranceMember" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_InternetServicesMember" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_ManufacturingMember" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_MarketingServicesMember" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_OfficeProductsMember" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_OilGasAndConsumableFuelsMember" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_OtherMember" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_RetailAndConsumerProductsMember" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_TransportationMember" order="17" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US" xlink:label="country_US"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MidwestMember" xlink:label="tslx_MidwestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_AU" xlink:label="country_AU"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NortheastMember" xlink:label="tslx_NortheastMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_CA" xlink:label="country_CA"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SouthMember" xlink:label="tslx_SouthMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_FI" xlink:label="country_FI"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_WestMember" xlink:label="tslx_WestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_DE" xlink:label="country_DE"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_LU" xlink:label="country_LU"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_NL" xlink:label="country_NL"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_NO" xlink:label="country_NO"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_SE" xlink:label="country_SE"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_GB" xlink:label="country_GB"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="srt_StatementGeographicalAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="tslx_PercentageOfInvestmentsAtFairValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_US" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="country_US" xlink:to="tslx_MidwestMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_AU" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="country_US" xlink:to="tslx_NortheastMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_CA" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="country_US" xlink:to="tslx_SouthMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_FI" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="country_US" xlink:to="tslx_WestMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_DE" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_LU" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_NL" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_NO" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_SE" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_GB" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueParentheticalDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_FI" xlink:label="country_FI"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:label="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="srt_StatementGeographicalAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="tslx_PercentageOfInvestmentsAtFairValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_FI" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="srt_RangeAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapOneMember" xlink:label="tslx_InterestRateSwapOneMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable" xlink:label="us-gaap_DerivativeTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems" xlink:label="us-gaap_DerivativeLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTwoMember" xlink:label="tslx_InterestRateSwapTwoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DerivativeNotionalAmountHeldDuringPeriod" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapThreeMember" xlink:label="tslx_InterestRateSwapThreeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapFourMember" xlink:label="tslx_InterestRateSwapFourMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapFiveMember" xlink:label="tslx_InterestRateSwapFiveMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapSixMember" xlink:label="tslx_InterestRateSwapSixMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapSevenMember" xlink:label="tslx_InterestRateSwapSevenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapEightMember" xlink:label="tslx_InterestRateSwapEightMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapNineMember" xlink:label="tslx_InterestRateSwapNineMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTenMember" xlink:label="tslx_InterestRateSwapTenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapElevenMember" xlink:label="tslx_InterestRateSwapElevenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTwelveMember" xlink:label="tslx_InterestRateSwapTwelveMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapThirteenMember" xlink:label="tslx_InterestRateSwapThirteenMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapOneMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="us-gaap_DerivativeTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeMaturityDates" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeInstrumentRiskAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapTwoMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="tslx_DerivativeNotionalAmountHeldDuringPeriod" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapThreeMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_PaymentsForHedgeInvestingActivities" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapFourMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_ProceedsFromHedgeInvestingActivities" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapFiveMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedTotalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapSixMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapSevenMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapEightMember" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapNineMember" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapTenMember" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapElevenMember" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapTwelveMember" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapThirteenMember" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember" xlink:label="us-gaap_InterestRateSwapMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:label="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable" xlink:label="us-gaap_DerivativeTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems" xlink:label="us-gaap_DerivativeLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain" xlink:label="us-gaap_PledgedStatusDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralMember" xlink:label="us-gaap_AssetPledgedAsCollateralMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseMember" xlink:label="us-gaap_InterestExpenseMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusAxis" xlink:label="us-gaap_PledgedStatusAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeForwardMember" xlink:label="us-gaap_ForeignExchangeForwardMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash" xlink:label="us-gaap_Cash"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_InterestRateSwapMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosureAbstract" xlink:to="us-gaap_DerivativeTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_NondesignatedMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_PledgedStatusDomain" xlink:to="us-gaap_AssetPledgedAsCollateralMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeInstrumentRiskAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_InterestExpenseMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_PledgedStatusAxis" xlink:to="us-gaap_PledgedStatusDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_ForeignExchangeForwardMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_DesignatedAsHedgingInstrumentMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_HedgingDesignationAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeFairValueOfDerivativeNet" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_IncomeStatementLocationAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_Cash" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DebtInstrumentAxis" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_PledgedStatusAxis" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeLineItems" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradingSecuritiesDebt" xlink:label="us-gaap_TradingSecuritiesDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="us-gaap_FairValueInputsLevel1Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestments" xlink:label="tslx_EquityAndOtherInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestments" xlink:label="tslx_StructuredCreditInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="us-gaap_InvestmentsFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwaps" xlink:label="tslx_InterestRateSwaps"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsFairValueDisclosureNet" xlink:label="tslx_InvestmentsFairValueDisclosureNet"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_TradingSecuritiesDebt" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel1Member" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_InvestmentTypeAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_EquityAndOtherInvestments" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_StructuredCreditInvestments" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_InvestmentsFairValueDisclosure" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_InterestRateSwaps" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_InvestmentsFairValueDisclosureNet" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsChangesInFairValueOfInvestmentsUsingLevel3InputsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList" xlink:label="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList" xlink:label="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_12"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_InvestmentTypeAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue_12" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsNetChangeInUnrealizedGainsOrLossesOnInvestmentsForWhichLevel3InputsWereUsedInDeterminingFairValueDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_InvestmentTypeAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestment" xlink:label="us-gaap_AlternativeInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueAxis" xlink:label="us-gaap_ValuationTechniqueAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputDiscountRateMember" xlink:label="us-gaap_MeasurementInputDiscountRateMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="us-gaap_ValuationTechniqueDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeApproachValuationTechniqueMember" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="us-gaap_MeasurementInputTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestmentMeasurementInput" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputComparabilityAdjustmentMember" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MarketApproachValuationTechniqueMember" xlink:label="us-gaap_MarketApproachValuationTechniqueMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_WeightedAverageMember" xlink:label="srt_WeightedAverageMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_AlternativeInvestment" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_ValuationTechniqueAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputDiscountRateMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_IncomeApproachValuationTechniqueMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_MeasurementInputTypeAxis" xlink:to="us-gaap_MeasurementInputTypeDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueAxis" xlink:to="us-gaap_ValuationTechniqueDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_AlternativeInvestmentMeasurementInput" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_InvestmentTypeAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputComparabilityAdjustmentMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_MarketApproachValuationTechniqueMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_MeasurementInputTypeAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_WeightedAverageMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="srt_RangeAxis" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsParenthe" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradingSecuritiesDebt" xlink:label="us-gaap_TradingSecuritiesDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueAxis" xlink:label="us-gaap_ValuationTechniqueAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="us-gaap_ValuationTechniqueDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AssetValuationWaterfallMember" xlink:label="tslx_AssetValuationWaterfallMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BlackScholesModelMember" xlink:label="tslx_BlackScholesModelMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CostModelMember" xlink:label="tslx_CostModelMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ValuationTechniqueCostOfInvestmentsMember" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_TradingSecuritiesDebt" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_ValuationTechniqueAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_AssetValuationWaterfallMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueAxis" xlink:to="us-gaap_ValuationTechniqueDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_InvestmentTypeAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_BlackScholesModelMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_CostModelMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_ValuationTechniqueDiscountedCashFlowMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_ValuationTechniqueCostOfInvestmentsMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfNotesDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayable" xlink:label="us-gaap_NotesPayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosuresAbstract" xlink:label="us-gaap_FairValueDisclosuresAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayableFairValueDisclosure" xlink:label="us-gaap_NotesPayableFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:to="us-gaap_NotesPayable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:to="us-gaap_DebtInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosuresAbstract" xlink:to="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:to="us-gaap_NotesPayableFairValueDisclosure" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:to="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ObligorGroupMember" xlink:label="srt_ObligorGroupMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AssetCoveragePercentage" xlink:label="tslx_AssetCoveragePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ThreeMonthLiborMember" xlink:label="tslx_ThreeMonthLiborMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="srt_ConsolidatedEntitiesAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnApril232027Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BaseRateMember" xlink:label="us-gaap_BaseRateMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnApril242029Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LineOfCreditFacilityExtendedDate" xlink:label="tslx_LineOfCreditFacilityExtendedDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember" xlink:label="us-gaap_LetterOfCreditMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LineOfCreditFacilityStatedMaturityDate" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit" xlink:label="us-gaap_LineOfCredit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="us-gaap_LettersOfCreditOutstandingAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RatioOfIndebtednessToNetCapital1" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdditionalAggregatePrincipalAmount" xlink:label="tslx_AdditionalAggregatePrincipalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="us-gaap_DebtInstrumentMaturityDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ExtinguishmentOfDebtAmount" xlink:label="us-gaap_ExtinguishmentOfDebtAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1" xlink:label="us-gaap_DebtConversionConvertedInstrumentAmount1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DebtConversionPrincipalAmount" xlink:label="tslx_DebtConversionPrincipalAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromUnsecuredNotesPayable" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" xlink:label="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="srt_ObligorGroupMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtInstrumentTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_AssetCoveragePercentage" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_VariableRateDomain" xlink:to="tslx_ThreeMonthLiborMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="srt_RangeAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnApril232027Member" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_BaseRateMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityCommitmentFeeAmount" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_VariableRateAxis" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="srt_ConsolidatedEntitiesAxis" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_GainsLossesOnExtinguishmentOfDebt" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentLineItems" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnApril242029Member" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_LineOfCreditFacilityExtendedDate" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_LetterOfCreditMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_LineOfCreditFacilityStatedMaturityDate" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCredit" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LettersOfCreditOutstandingAmount" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_RatioOfIndebtednessToNetCapital1" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_StockholdersEquity" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" order="17" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_AdditionalAggregatePrincipalAmount" order="18" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentMaturityDate" order="19" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeMaturityDates" order="20" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentConvertibleConversionPrice1" order="21" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_ExtinguishmentOfDebtAmount" order="22" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtConversionConvertedInstrumentAmount1" order="23" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtConversionConvertedInstrumentSharesIssued1" order="24" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_DebtConversionPrincipalAmount" order="25" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" order="26" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" order="27" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_ProceedsFromUnsecuredNotesPayable" order="28" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" order="29" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" order="30" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" order="31" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" order="32" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" order="33" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SwapSettlement" xlink:label="tslx_SwapSettlement"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestAndDebtExpense" xlink:label="us-gaap_InterestAndDebtExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityAverageOutstandingAmount" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtWeightedAverageInterestRateOverTime" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtInstrumentTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_InterestExpenseDebt" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_AmortizationOfFinancingCosts" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_SwapSettlement" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_InterestAndDebtExpense" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityAverageOutstandingAmount" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OriginalIssueDiscountNetOfAccretion" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfAnEffectiveHedge" xlink:label="tslx_FairValueOfAnEffectiveHedge"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtInstrumentTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentCarryingAmount" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_OriginalIssueDiscountNetOfAccretion" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DeferredFinanceCostsNet" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_FairValueOfAnEffectiveHedge" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LongTermDebt" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfDebtObligationsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtInstrumentTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentCarryingAmount" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LongTermDebt" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfDebtObligationsParentheticalDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="us-gaap_DebtDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtDisclosureAbstract" xlink:to="us-gaap_DebtInstrumentTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="srt_RangeAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentLineItems" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AlaskaBidcoOyMember" xlink:label="tslx_AlaskaBidcoOyMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawMember" xlink:label="tslx_DelayedDrawMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="srt_ConsolidatedEntitiesAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PurchaseCommitmentToFundInvestment" xlink:label="tslx_PurchaseCommitmentToFundInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AlphaMidcoIncMember" xlink:label="tslx_AlphaMidcoIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverMember" xlink:label="tslx_RevolverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AmericanAchievementCorpMember" xlink:label="tslx_AmericanAchievementCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawAndRevolverMember" xlink:label="tslx_DelayedDrawAndRevolverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ApteanIncMember" xlink:label="tslx_ApteanIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawAndMembershipInterestMember" xlink:label="tslx_DelayedDrawAndMembershipInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ArrowbuyerIncMember" xlink:label="tslx_ArrowbuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverAndPartnershipInterestMember" xlink:label="tslx_RevolverAndPartnershipInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ArtisanBidcoIncMember" xlink:label="tslx_ArtisanBidcoIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverEquityMember" xlink:label="tslx_RevolverEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AsgIiLlcMember" xlink:label="tslx_AsgIiLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawEquityMember" xlink:label="tslx_DelayedDrawEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AvalaraIncMember" xlink:label="tslx_AvalaraIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawRevolverPreferredEquityMember" xlink:label="tslx_DelayedDrawRevolverPreferredEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AxonifyIncMember" xlink:label="tslx_AxonifyIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawRevolverEquityMember" xlink:label="tslx_DelayedDrawRevolverEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AzuriteIntermediateHoldingsIncMember" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BabylonFincoLimitedMember" xlink:label="tslx_BabylonFincoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BanyanSoftwareHoldingsLlcMember" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BayshoreIntermediate2LPMember" xlink:label="tslx_BayshoreIntermediate2LPMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BCTOAcePurchaserIncMember" xlink:label="tslx_BCTOAcePurchaserIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BctoBluebillBuyerIncMember" xlink:label="tslx_BctoBluebillBuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BearOpCoLLCMember" xlink:label="tslx_BearOpCoLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BenNevisMidcoLimitedMember" xlink:label="tslx_BenNevisMidcoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BlueSnapIncMember" xlink:label="tslx_BlueSnapIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BtrsHoldingIncMember" xlink:label="tslx_BtrsHoldingIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CordanceOperationsLlcMember" xlink:label="tslx_CordanceOperationsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CoupaHoldingsLLCMember" xlink:label="tslx_CoupaHoldingsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CrewlineBuyerIncMember" xlink:label="tslx_CrewlineBuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DiscoParentIncMember" xlink:label="tslx_DiscoParentIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DyeDurhamCorpMember" xlink:label="tslx_DyeDurhamCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EDBParentLLCMember" xlink:label="tslx_EDBParentLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EdgeBidcoBVMember" xlink:label="tslx_EdgeBidcoBVMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ElysianFincoLtdMember" xlink:label="tslx_ElysianFincoLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EmploymentHeroHoldingsPtyLtdMember" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EMSLinqIncMember" xlink:label="tslx_EMSLinqIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ErlingLuxBidcoSarlMember" xlink:label="tslx_ErlingLuxBidcoSarlMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ExtraHopNetworksIncMember" xlink:label="tslx_ExtraHopNetworksIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FullsteamOperationsLlcMember" xlink:label="tslx_FullsteamOperationsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ForeScoutTechnologiesIncMember" xlink:label="tslx_ForeScoutTechnologiesIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_GalileoParentincMember" xlink:label="tslx_GalileoParentincMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HeritageEnvironmentalServicesIncMember" xlink:label="tslx_HeritageEnvironmentalServicesIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HippoXpaBidcoAbMember" xlink:label="tslx_HippoXpaBidcoAbMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HirevueIncMember" xlink:label="tslx_HirevueIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HornetsecurityHoldingGmbhMember" xlink:label="tslx_HornetsecurityHoldingGmbhMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IbisIntermediateCoMember" xlink:label="tslx_IbisIntermediateCoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IRGSEHoldingCorpMember" xlink:label="tslx_IRGSEHoldingCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_KangarooBidcoASMember" xlink:label="tslx_KangarooBidcoASMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_KyribaCorpMember" xlink:label="tslx_KyribaCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LaramieEnergyLLCMember" xlink:label="tslx_LaramieEnergyLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LeantaasHoldingsIncMember" xlink:label="tslx_LeantaasHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LucidworksIncMember" xlink:label="tslx_LucidworksIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MarcuraEquitiesLtdMember" xlink:label="tslx_MarcuraEquitiesLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetwrixCorpMember" xlink:label="tslx_NetwrixCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OutsystemsLuxcoMember" xlink:label="tslx_OutsystemsLuxcoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PassportLabsIncMember" xlink:label="tslx_PassportLabsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PdiTaHoldingsIncMember" xlink:label="tslx_PdiTaHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PingIdentityCorporationMember" xlink:label="tslx_PingIdentityCorporationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PrimeRevenueIncMember" xlink:label="tslx_PrimeRevenueIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_Project44IncMember" xlink:label="tslx_Project44IncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RapidDataGmbhUnternehmensberatungMember" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ReliaQuestHoldingsLLCMember" xlink:label="tslx_ReliaQuestHoldingsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SkylarkUkDebtcoLimitedMember" xlink:label="tslx_SkylarkUkDebtcoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SlBuyerCorpMember" xlink:label="tslx_SlBuyerCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TangoManagementConsultingLLCMember" xlink:label="tslx_TangoManagementConsultingLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TRPAssetsLLCMember" xlink:label="tslx_TRPAssetsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TruckLiteCoLlcMember" xlink:label="tslx_TruckLiteCoLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_WranglerTopcoLlcMember" xlink:label="tslx_WranglerTopcoLlcMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AlaskaBidcoOyMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_LossContingenciesTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesTable" xlink:to="srt_ConsolidatedEntitiesAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="tslx_PurchaseCommitmentToFundInvestment" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AlphaMidcoIncMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_RevolverMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_FinancialInstrumentAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AmericanAchievementCorpMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawAndRevolverMember" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_LossContingenciesLineItems" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ApteanIncMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawAndMembershipInterestMember" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ArrowbuyerIncMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_RevolverAndPartnershipInterestMember" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ArtisanBidcoIncMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_RevolverEquityMember" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AsgIiLlcMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawEquityMember" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AvalaraIncMember" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawRevolverPreferredEquityMember" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AxonifyIncMember" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawRevolverEquityMember" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AzuriteIntermediateHoldingsIncMember" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BabylonFincoLimitedMember" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BanyanSoftwareHoldingsLlcMember" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BayshoreIntermediate2LPMember" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BCTOAcePurchaserIncMember" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BctoBluebillBuyerIncMember" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BearOpCoLLCMember" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BenNevisMidcoLimitedMember" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BlueSnapIncMember" order="17" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BtrsHoldingIncMember" order="18" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_CordanceOperationsLlcMember" order="19" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_CoupaHoldingsLLCMember" order="20" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_CrewlineBuyerIncMember" order="21" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_DiscoParentIncMember" order="22" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_DyeDurhamCorpMember" order="23" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EDBParentLLCMember" order="24" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EdgeBidcoBVMember" order="25" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ElysianFincoLtdMember" order="26" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EmploymentHeroHoldingsPtyLtdMember" order="27" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EMSLinqIncMember" order="28" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ErlingLuxBidcoSarlMember" order="29" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ExtraHopNetworksIncMember" order="30" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_FullsteamOperationsLlcMember" order="31" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ForeScoutTechnologiesIncMember" order="32" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_GalileoParentincMember" order="33" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HeritageEnvironmentalServicesIncMember" order="34" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HippoXpaBidcoAbMember" order="35" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HirevueIncMember" order="36" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HornetsecurityHoldingGmbhMember" order="37" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_IbisIntermediateCoMember" order="38" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_IRGSEHoldingCorpMember" order="39" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_KangarooBidcoASMember" order="40" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_KyribaCorpMember" order="41" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_LaramieEnergyLLCMember" order="42" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_LeantaasHoldingsIncMember" order="43" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_LucidworksIncMember" order="44" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_MarcuraEquitiesLtdMember" order="45" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_NetwrixCorpMember" order="46" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_OutsystemsLuxcoMember" order="47" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PassportLabsIncMember" order="48" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PdiTaHoldingsIncMember" order="49" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PingIdentityCorporationMember" order="50" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PrimeRevenueIncMember" order="51" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_Project44IncMember" order="52" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_RapidDataGmbhUnternehmensberatungMember" order="53" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ReliaQuestHoldingsLLCMember" order="54" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_SkylarkUkDebtcoLimitedMember" order="55" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_SlBuyerCorpMember" order="56" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_TangoManagementConsultingLLCMember" order="57" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_TRPAssetsLLCMember" order="58" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_TruckLiteCoLlcMember" order="59" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_WranglerTopcoLlcMember" order="60" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitment" xlink:label="us-gaap_OtherCommitment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnfundedLoanCommitmentMember" xlink:label="us-gaap_UnfundedLoanCommitmentMember"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_CommitmentsAndContingenciesDisclosureAbstract" xlink:to="us-gaap_LossContingenciesTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_OtherCommitment" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:to="us-gaap_UnfundedLoanCommitmentMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_LossContingenciesLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="us-gaap_ScheduleOfStockByClassTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems" xlink:label="us-gaap_ClassOfStockLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract" xlink:label="us-gaap_EquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="us-gaap_OverAllotmentOptionMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionOriginalDebtAmount1" xlink:label="us-gaap_DebtConversionOriginalDebtAmount1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CurrentMarketPricePerSharePercentage" xlink:label="tslx_CurrentMarketPricePerSharePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramPeriodInForce1" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramExpirationDate" xlink:label="us-gaap_StockRepurchaseProgramExpirationDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="us-gaap_TreasuryStockSharesAcquired"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_DebtInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_CommonStockSharesIssued" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_CommonStockMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_ScheduleOfStockByClassTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_OverAllotmentOptionMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_StatementEquityComponentsAxis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_SharesIssuedPricePerShare" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_ClassOfStockLineItems" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_DebtConversionOriginalDebtAmount1" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="tslx_CurrentMarketPricePerSharePercentage" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockRepurchaseProgramAuthorizedAmount1" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockRepurchaseProgramPeriodInForce1" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockRepurchaseProgramExpirationDate" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_TreasuryStockSharesAcquired" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_TreasuryStockAcquiredAverageCostPerShare" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_TreasuryStockValueAcquiredCostMethod" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsScheduleOfSharesIssuedToStockholdersDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="us-gaap_ScheduleOfStockByClassTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAxis" xlink:label="us-gaap_DividendsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems" xlink:label="us-gaap_ClassOfStockLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDomain" xlink:label="us-gaap_DividendsDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityAbstract" xlink:label="us-gaap_EquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BaseDividendMember" xlink:label="tslx_BaseDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SupplementalDividendMember" xlink:label="tslx_SupplementalDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_DividendsAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsAxis" xlink:to="us-gaap_DividendsDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EquityAbstract" xlink:to="us-gaap_ScheduleOfStockByClassTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_BaseDividendMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_ClassOfStockLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_SupplementalDividendMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerCommonShareDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="us-gaap_EarningsPerShareBasicAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="us-gaap_EarningsPerShareAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:to="us-gaap_EarningsPerShareBasicAbstract" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareAbstract" xlink:to="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_ProfitLoss" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:to="us-gaap_DebtInstrumentAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:to="tslx_EarningsPerShareBasicAndDilutedLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" order="2.0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_EarningsPerShareBasic" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_EarningsPerShareDiluted" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsSummaryOfDividendsDeclaredDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAxis" xlink:label="us-gaap_DividendsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDomain" xlink:label="us-gaap_DividendsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SupplementalDividendMember" xlink:label="tslx_SupplementalDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAbstract" xlink:label="us-gaap_DividendsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableTable" xlink:label="us-gaap_DividendsPayableTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableLineItems" xlink:label="us-gaap_DividendsPayableLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BaseDividendMember" xlink:label="tslx_BaseDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableNature" xlink:label="us-gaap_DividendsPayableNature"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendPayableDateToBePaidDayMonthAndYear" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableAmountPerShare" xlink:label="us-gaap_DividendsPayableAmountPerShare"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsAxis" xlink:to="us-gaap_DividendsDomain" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_SupplementalDividendMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsAbstract" xlink:to="us-gaap_DividendsPayableTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableTable" xlink:to="us-gaap_DividendsAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_BaseDividendMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableNature" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableTable" xlink:to="us-gaap_DividendsPayableLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/verboseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendPayableDateToBePaidDayMonthAndYear" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableAmountPerShare" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OrdinaryIncome" xlink:label="tslx_OrdinaryIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LongTermCapitalGains" xlink:label="tslx_LongTermCapitalGains"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredDuringThePeriod" xlink:label="tslx_DividendsDeclaredDuringThePeriod"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_OrdinaryIncome" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_LongTermCapitalGains" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_DividendsDeclaredDuringThePeriod" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsParentheticalDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder" xlink:label="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxBasisComponentsOfDistributableEarningsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UndistributedNetInvestmentIncomeTaxBasis" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UndistributedNetRealizedGainsTaxBasis" xlink:label="tslx_UndistributedNetRealizedGainsTaxBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetUnrealizedGainsOnInvestments" xlink:label="tslx_NetUnrealizedGainsOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherTemporaryDifferences" xlink:label="tslx_OtherTemporaryDifferences"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DistributedEarnings" xlink:label="us-gaap_DistributedEarnings"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_UndistributedNetInvestmentIncomeTaxBasis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_UndistributedNetRealizedGainsTaxBasis" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_NetUnrealizedGainsOnInvestments" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_OtherTemporaryDifferences" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_DistributedEarnings" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfReconciliationIncreaseInNetAssetsDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdjustmentsAbstract" xlink:label="tslx_AdjustmentsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" xlink:label="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherIncomeForTaxPurposesNotBook" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DeferredOrganizationCosts" xlink:label="tslx_DeferredOrganizationCosts"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherExpensesNotCurrentlyDeductible" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherBookTaxDifferences" xlink:label="tslx_OtherBookTaxDifferences"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxableIncome" xlink:label="tslx_TaxableIncome"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_OtherIncomeForTaxPurposesNotBook" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="tslx_AdjustmentsAbstract" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_DeferredOrganizationCosts" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_OtherExpensesNotCurrentlyDeductible" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_OtherBookTaxDifferences" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="tslx_AdjustmentsAbstract" xlink:to="tslx_TaxableIncome" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardLineItems" xlink:label="us-gaap_TaxCreditCarryforwardLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInDistributableEarnings" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardTable" xlink:label="us-gaap_TaxCreditCarryforwardTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxDisclosureAbstract" xlink:label="us-gaap_IncomeTaxDisclosureAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInAdditionalPaidInCapital" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NumberOfInvestments" xlink:label="tslx_NumberOfInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredTaxAssetsGross" xlink:label="us-gaap_DeferredTaxAssetsGross"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" xlink:label="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxCostOfInvestments" xlink:label="tslx_TaxCostOfInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpenseForFederalExciseTax" xlink:label="tslx_NetExpenseForFederalExciseTax"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_IncreaseDecreaseInDistributableEarnings" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardTable" xlink:to="srt_RangeAxis" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_IncomeTaxDisclosureAbstract" xlink:to="us-gaap_TaxCreditCarryforwardTable" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_IncreaseDecreaseInAdditionalPaidInCapital" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardTable" xlink:to="us-gaap_TaxCreditCarryforwardLineItems" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/label"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_CurrentIncomeTaxExpenseBenefit" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_DeferredIncomeTaxExpenseBenefit" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2009/role/negatedLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_NumberOfInvestments" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_DeferredTaxAssetsGross" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_TaxCostOfInvestments" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_NetExpenseForFederalExciseTax" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetAssetValuePerShare" xlink:label="us-gaap_NetAssetValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IssuanceOfCommonStockNetOfOfferingCosts" xlink:label="tslx_IssuanceOfCommonStockNetOfOfferingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyRepurchaseOfDebtPerShare" xlink:label="tslx_InvestmentCompanyRepurchaseOfDebtPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendDeclaredFromRealizedGainsPerShare" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetAssetValuePerShare" xlink:label="us-gaap_NetAssetValuePerShare_12"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PerShareMarketValueAtEndPeriod" xlink:label="tslx_PerShareMarketValueAtEndPeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends" xlink:label="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TotalReturnBasedOnMarketValue" xlink:label="tslx_TotalReturnBasedOnMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TotalReturnBasedOnNetAssetValue" xlink:label="tslx_TotalReturnBasedOnNetAssetValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation" xlink:label="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" xlink:label="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueNetAssetLiability" xlink:label="us-gaap_FairValueNetAssetLiability"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_NetAssetValuePerShare" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodStartLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" order="1" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" order="2" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" order="3" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_IssuanceOfCommonStockNetOfOfferingCosts" order="4" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" order="5" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" order="6" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" order="7" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_InvestmentCompanyRepurchaseOfDebtPerShare" order="8" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" order="9" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_DividendDeclaredFromRealizedGainsPerShare" order="10" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" order="11" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/totalLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_NetAssetValuePerShare_12" order="12" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/periodEndLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_PerShareMarketValueAtEndPeriod" order="13" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends" order="14" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_TotalReturnBasedOnMarketValue" order="15" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="tslx_TotalReturnBasedOnNetAssetValue" order="16" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_SharesOutstanding" order="17" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyExpenseRatioBeforeIncentiveAllocation" order="18" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossRatio" order="19" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyIncentiveFeeToAverageNetAssets" order="20" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_FairValueNetAssetLiability" order="21" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:presentationLink xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingParentheticalDetails" xlink:title="presentationLink" xlink:type="extended">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:label="us-gaap_InvestmentCompanyFinancialHighlightsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver" xlink:label="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver"/>
          <link:presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="us-gaap_InvestmentCompanyFinancialHighlightsAbstract" xlink:to="us-gaap_InvestmentCompanyExpenseRatioVoluntaryFeeWaiver" order="0" priority="2" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel"/>
        </link:presentationLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnaudited">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAbstract" xlink:label="us-gaap_LiabilitiesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeePayable" xlink:label="us-gaap_ManagementFeePayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestReceivable" xlink:label="us-gaap_InterestReceivable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssets" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherPayablesToAffiliate" xlink:label="tslx_OtherPayablesToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities" xlink:label="us-gaap_OtherLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsNet" xlink:label="us-gaap_AssetsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetAssetValuePerShare" xlink:label="us-gaap_NetAssetValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_InvestmentOwnedAtFairValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_LongTermDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_PreferredStockValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_AssetsAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_ManagementFeePayable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_CommonStockValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_InterestReceivable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommitmentsAndContingencies" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_PrepaidExpenseAndOtherAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_TreasuryStockValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquityAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_Assets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="tslx_OtherPayablesToAffiliate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_OtherLiabilities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_AssetsNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NetAssetValuePerShare" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LiabilitiesAbstract" xlink:to="us-gaap_Liabilities" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnauditedParenthetical">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtCost" xlink:label="us-gaap_InvestmentOwnedAtCost"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RestrictedCash" xlink:label="us-gaap_RestrictedCash"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonShares" xlink:label="us-gaap_TreasuryStockCommonShares"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtCost" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_RestrictedCash" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DeferredFinanceCostsNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesAuthorized" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesIssued" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_PreferredStockSharesOutstanding" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesAuthorized" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesIssued" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_CommonStockSharesOutstanding" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_TreasuryStockCommonShares" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfOperationsUnaudited">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:label="tslx_UnRealizedInvestmentGainsLossesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnInvestments" xlink:label="us-gaap_UnrealizedGainLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:label="us-gaap_RealizedInvestmentGainsLossesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLosses" xlink:label="us-gaap_RealizedInvestmentGainsLosses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpenseAbstract" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledNonAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledNonAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeInterest" xlink:label="us-gaap_InvestmentIncomeInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeeExpense" xlink:label="us-gaap_ManagementFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfDerivatives" xlink:label="us-gaap_GainLossOnSaleOfDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NonControlledAffiliatedInvestmentsMember" xlink:label="tslx_NonControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaidInKindInterestIncome" xlink:label="tslx_PaidInKindInterestIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncome" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ControlledAffiliatedInvestmentsMember" xlink:label="tslx_ControlledAffiliatedInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeDividend" xlink:label="us-gaap_InvestmentIncomeDividend"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainsLossesOnIncomeTaxProvision" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGains" xlink:label="tslx_IncentiveFeesOnNetCapitalGains"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncome" xlink:label="us-gaap_OtherNonoperatingIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfessionalFees" xlink:label="us-gaap_ProfessionalFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet" xlink:label="us-gaap_InvestmentIncomeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpenseDirectorsFees" xlink:label="us-gaap_NoninterestExpenseDirectorsFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherGeneralAndAdministrativeExpense" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementAndIncentiveFeeWaived" xlink:label="tslx_ManagementAndIncentiveFeeWaived"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpense" xlink:label="tslx_NetExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_UnrealizedGainLossOnInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_InterestExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_RealizedInvestmentGainsLosses" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_NonoperatingIncomeExpenseAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:to="tslx_UnRealizedInvestmentGainsLossesAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledNonAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_InvestmentIncomeInterest" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_ManagementFeeExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_GainLossOnSaleOfDerivatives" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_OperatingExpensesAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" xlink:to="us-gaap_RealizedInvestmentGainsLossesAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_NonControlledAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="tslx_PaidInKindInterestIncome" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncome" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossRealized" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_ControlledAffiliatedInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_InvestmentIncomeDividend" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="tslx_UnrealizedGainsLossesOnIncomeTaxProvision" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_IncentiveFeesOnNetCapitalGains" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RealizedInvestmentGainsLossesAbstract" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_IncomeTaxExpenseBenefit" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_OtherNonoperatingIncome" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_UnRealizedInvestmentGainsLossesAbstract" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_ProfessionalFees" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentIncomeNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_NonoperatingIncomeExpenseAbstract" xlink:to="us-gaap_NonoperatingIncomeExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_NoninterestExpenseDirectorsFees" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrencyAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OtherGeneralAndAdministrativeExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpenses" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_ProfitLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_ManagementAndIncentiveFeeWaived" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_EarningsPerShareBasic" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="tslx_NetExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_EarningsPerShareDiluted" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnaudited">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentDueDate" xlink:label="tslx_InvestmentDueDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAcquisitionDate" xlink:label="us-gaap_InvestmentAcquisitionDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentBasisSpreadVariableRate" xlink:label="us-gaap_InvestmentBasisSpreadVariableRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentInterestRate" xlink:label="us-gaap_InvestmentInterestRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentInterestRatePaidInKind" xlink:label="us-gaap_InvestmentInterestRatePaidInKind"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtCost" xlink:label="us-gaap_InvestmentOwnedAtCost"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedPercentOfNetAssets" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeBasisSpreadOnVariableRate" xlink:label="us-gaap_DerivativeBasisSpreadOnVariableRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateDerivativesAtFairValueNet" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" xlink:label="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeGainLossOnDerivativeNet" xlink:label="us-gaap_DerivativeGainLossOnDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset" xlink:label="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PartnershipInterestOwnershipPercentage" xlink:label="tslx_PartnershipInterestOwnershipPercentage"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentDueDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentAcquisitionDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentBasisSpreadVariableRate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentInterestRate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentInterestRatePaidInKind" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtCost" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtFairValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedPercentOfNetAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeBasisSpreadOnVariableRate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeMaturityDates" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InterestRateDerivativesAtFairValueNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeGainLossOnDerivativeNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeLiabilityCollateralRightToReclaimCashOffset" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeFairValueOfDerivativeNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PartnershipInterestOwnershipPercentage" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParenthetical">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DomesticCountryMember" xlink:label="us-gaap_DomesticCountryMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentDueDate" xlink:label="tslx_InvestmentDueDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateDerivativesAtFairValueNet" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNonQualifyingAssets" xlink:label="tslx_PercentageOfNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsOwnedEstimatedCostBasis" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainOnInvestments" xlink:label="tslx_UnrealizedGainOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedLossOnInvestments" xlink:label="tslx_UnrealizedLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PartnershipInterestOwnershipPercentage" xlink:label="tslx_PartnershipInterestOwnershipPercentage"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxAuthorityDomain" xlink:to="us-gaap_DomesticCountryMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_NondesignatedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_HedgingDesignationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentDueDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_IncomeTaxAuthorityAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InterestRateDerivativesAtFairValueNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PercentageOfNonQualifyingAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsOwnedEstimatedCostBasis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UnrealizedGainOnInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UnrealizedLossOnInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PartnershipInterestOwnershipPercentage" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedScheduleOfInvestmentsUnauditedParentheticalDefault">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="us-gaap_IncomeTaxAuthorityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DomesticCountryMember" xlink:label="us-gaap_DomesticCountryMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" xlink:label="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxAuthorityAxis" xlink:label="us-gaap_IncomeTaxAuthorityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentDueDate" xlink:label="tslx_InvestmentDueDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateDerivativesAtFairValueNet" xlink:label="us-gaap_InterestRateDerivativesAtFairValueNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNonQualifyingAssets" xlink:label="tslx_PercentageOfNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" xlink:label="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" xlink:label="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsOwnedEstimatedCostBasis" xlink:label="tslx_InvestmentsOwnedEstimatedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainOnInvestments" xlink:label="tslx_UnrealizedGainOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedLossOnInvestments" xlink:label="tslx_UnrealizedLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" xlink:label="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" xlink:label="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PartnershipInterestOwnershipPercentage" xlink:label="tslx_PartnershipInterestOwnershipPercentage"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeTaxAuthorityDomain" xlink:to="us-gaap_DomesticCountryMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedUnderlyingFaceAmountAtMarketValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeTaxAuthorityAxis" xlink:to="us-gaap_IncomeTaxAuthorityDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_NondesignatedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentDueDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_HedgingDesignationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_IncomeTaxAuthorityAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InterestRateDerivativesAtFairValueNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PercentageOfNonQualifyingAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsOwnedEstimatedCostBasis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UnrealizedGainOnInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_UnrealizedLossOnInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_PartnershipInterestOwnershipPercentage" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnaudited">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" xlink:label="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" xlink:label="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedAtFairValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossAdditions" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentsInAndAdvancesToAffiliatesAtFairValueGrossReductions" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParenthetical">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIdentifierAxis" xlink:label="us-gaap_InvestmentIdentifierAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIdentifierAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedScheduleOfInvestmentsAffiliatedInvestmentsUnauditedParentheticalDefault">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedBalanceShares" xlink:label="us-gaap_InvestmentOwnedBalanceShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationDomain" xlink:label="us-gaap_InvestmentIssuerAffiliationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentAffiliatedIssuerControlledMember" xlink:label="us-gaap_InvestmentAffiliatedIssuerControlledMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIssuerAffiliationAxis" xlink:label="us-gaap_InvestmentIssuerAffiliationAxis"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentOwnedBalanceShares" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentIssuerAffiliationDomain" xlink:to="us-gaap_InvestmentAffiliatedIssuerControlledMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentIssuerAffiliationAxis" xlink:to="us-gaap_InvestmentIssuerAffiliationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_InvestmentIssuerAffiliationAxis" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfChangesInNetAssetsUnaudited">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:label="srt_CumulativeEffectPeriodOfAdoptionDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" xlink:label="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockCommonMember" xlink:label="us-gaap_TreasuryStockCommonMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet" xlink:label="us-gaap_InvestmentIncomeNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Dividends" xlink:label="us-gaap_Dividends"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxReclassificationOfStockholdersEquity" xlink:label="tslx_TaxReclassificationOfStockholdersEquity"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_CommonStockMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:to="srt_CumulativeEffectPeriodOfAdoptionDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_CumulativeEffectPeriodOfAdoptionAxis" xlink:to="srt_CumulativeEffectPeriodOfAdoptionDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementEquityComponentsAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockholdersEquity" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_CumulativeEffectPeriodOfAdoptionDomain" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAdjustmentMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_TreasuryStockCommonMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_StatementTable" xlink:to="srt_CumulativeEffectPeriodOfAdoptionAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_SharesOutstanding" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_AdditionalPaidInCapitalMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_InvestmentIncomeNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_RetainedEarningsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueNewIssues" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueDividendReinvestmentPlan" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_Dividends" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_StatementLineItems" xlink:to="tslx_TaxReclassificationOfStockholdersEquity" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/cef/role/RiskOnly">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/cef/2023/cef-2023.xsd#cef_AllRisksMember" xlink:label="cef_AllRisksMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RisksAssociatedWithChangesInInterestRatesMember" xlink:label="tslx_RisksAssociatedWithChangesInInterestRatesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RisksAssociatedWithConflictsOfInterestMember" xlink:label="tslx_RisksAssociatedWithConflictsOfInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" xlink:label="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LegislationAllowsToIncurAdditionalLeverageMember" xlink:label="tslx_LegislationAllowsToIncurAdditionalLeverageMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" xlink:label="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" xlink:label="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" xlink:label="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" xlink:label="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_RisksAssociatedWithChangesInInterestRatesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_RisksAssociatedWithConflictsOfInterestMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_LegislationAllowsToIncurAdditionalLeverageMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="cef_AllRisksMember" xlink:to="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://xbrl.sec.gov/cef/role/SecurityOnly">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwentyTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyThreeNotesMember" xlink:label="tslx_TwentyTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyFourNotesMember" xlink:label="tslx_TwentyTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentySixNotesMember" xlink:label="tslx_TwentyTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyEightNotesMember" xlink:label="tslx_TwentyTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwentyTwentyNineNotesMember" xlink:label="tslx_TwentyTwentyNineNotesMember"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyTwoConvertibleNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyThreeNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwentyTwentyNineNotesMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SignificantAccountingPoliciesLineItems" xlink:label="tslx_SignificantAccountingPoliciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SignificantAccountingPoliciesTable" xlink:label="tslx_SignificantAccountingPoliciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AccountingStandardsUpdate202206Member" xlink:label="tslx_AccountingStandardsUpdate202206Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="us-gaap_TypeOfAdoptionMember_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" xlink:label="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NondeductibleFederalExciseTaxPercentage" xlink:label="tslx_NondeductibleFederalExciseTaxPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" xlink:label="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect" xlink:label="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_SignificantAccountingPoliciesTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="tslx_SignificantAccountingPoliciesTable" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TypeOfAdoptionMember" xlink:to="tslx_AccountingStandardsUpdate202206Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_TypeOfAdoptionMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_TypeOfAdoptionMember_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_NondeductibleFederalExciseTaxPercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdopted" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateAdoptionDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_SignificantAccountingPoliciesLineItems" xlink:to="us-gaap_ChangeInAccountingPrincipleAccountingStandardsUpdateImmaterialEffect" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureAgreementsAndRelatedPartyTransactionsAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="us-gaap_RelatedPartyTransactionLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AgreementTerminationPeriodWithoutPenalty" xlink:label="tslx_AgreementTerminationPeriodWithoutPenalty"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="srt_ScenarioUnspecifiedDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioForecastMember" xlink:label="srt_ScenarioForecastMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:label="us-gaap_RelatedAndNonrelatedPartyStatusDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdviserMember" xlink:label="tslx_AdviserMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementScenarioAxis" xlink:label="srt_StatementScenarioAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="srt_ScenarioUnspecifiedDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="us-gaap_RelatedPartyTransactionDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdministrationAgreementMember" xlink:label="tslx_AdministrationAgreementMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyMember" xlink:label="us-gaap_RelatedPartyMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="us-gaap_RelatedPartyTransactionAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="us-gaap_RelatedPartyTransactionDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" xlink:label="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LeverageWaiverMember" xlink:label="tslx_LeverageWaiverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentAdvisoryAgreementMember" xlink:label="tslx_InvestmentAdvisoryAgreementMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" xlink:label="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeeExpense" xlink:label="us-gaap_ManagementFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" xlink:label="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementFeeWaiverHurdle" xlink:label="tslx_ManagementFeeWaiverHurdle"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" xlink:label="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" xlink:label="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" xlink:label="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" xlink:label="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" xlink:label="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:label="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" xlink:label="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" xlink:label="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfIncentiveFeeRate" xlink:label="tslx_PercentageOfIncentiveFeeRate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" xlink:label="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Investments" xlink:label="us-gaap_Investments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncentiveFeeExpense" xlink:label="us-gaap_IncentiveFeeExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesRealizedAndPayableToAdvisor" xlink:label="tslx_IncentiveFeesRealizedAndPayableToAdvisor"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncome" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" xlink:label="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_AgreementTerminationPeriodWithoutPenalty" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="srt_ScenarioForecastMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusAxis" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="tslx_AdviserMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_ScenarioUnspecifiedDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_ScenarioUnspecifiedDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="tslx_AdministrationAgreementMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedAndNonrelatedPartyStatusDomain" xlink:to="us-gaap_RelatedPartyMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_RelatedPartyTransactionAxis" xlink:to="us-gaap_RelatedPartyTransactionDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_RelatedPartyTransactionAxis" xlink:to="us-gaap_RelatedPartyTransactionDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedPartyTransactionAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="tslx_LeverageWaiverMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionDomain" xlink:to="tslx_InvestmentAdvisoryAgreementMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="srt_StatementScenarioAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_ManagementFeeExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_RelatedAndNonrelatedPartyStatusAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_ManagementFeeWaiverHurdle" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ScenarioUnspecifiedDomain" xlink:to="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_SubsequentEventTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_IncomeStatementLocationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="19" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfIncentiveFeeRate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="20" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="21" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_Investments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="22" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_IncentiveFeeExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="23" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_IncentiveFeesRealizedAndPayableToAdvisor" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="24" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncome" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="25" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfInvestmentsAtFairValueDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestmentsMember" xlink:label="tslx_StructuredCreditInvestmentsMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_FinancialInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_FirstLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecurities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_SecondLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_MezzanineDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_EquityAndOtherInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_StructuredCreditInvestmentsMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfIndustryCompositionOfInvestmentsAtFairValueDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesByIndustryAxis" xlink:label="us-gaap_EquitySecuritiesByIndustryAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesIndustryMember" xlink:label="us-gaap_EquitySecuritiesIndustryMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesIndustryMember" xlink:label="us-gaap_EquitySecuritiesIndustryMember_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AutomotiveMember" xlink:label="tslx_AutomotiveMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BusinessServicesMember" xlink:label="tslx_BusinessServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ChemicalsMember" xlink:label="tslx_ChemicalsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CommunicationsMember" xlink:label="tslx_CommunicationsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EducationMember" xlink:label="tslx_EducationMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialServicesSectorMember" xlink:label="us-gaap_FinancialServicesSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HealthcareSectorMember" xlink:label="us-gaap_HealthcareSectorMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HotelGamingAndLeisureMember" xlink:label="tslx_HotelGamingAndLeisureMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HumanResourceSupportServicesMember" xlink:label="tslx_HumanResourceSupportServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InsuranceMember" xlink:label="tslx_InsuranceMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InternetServicesMember" xlink:label="tslx_InternetServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManufacturingMember" xlink:label="tslx_ManufacturingMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MarketingServicesMember" xlink:label="tslx_MarketingServicesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OfficeProductsMember" xlink:label="tslx_OfficeProductsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OilGasAndConsumableFuelsMember" xlink:label="tslx_OilGasAndConsumableFuelsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherMember" xlink:label="tslx_OtherMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RetailAndConsumerProductsMember" xlink:label="tslx_RetailAndConsumerProductsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TransportationMember" xlink:label="tslx_TransportationMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="us-gaap_EquitySecuritiesByIndustryAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="tslx_PercentageOfInvestmentsAtFairValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_EquitySecuritiesByIndustryAxis" xlink:to="us-gaap_EquitySecuritiesIndustryMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_EquitySecuritiesByIndustryAxis" xlink:to="us-gaap_EquitySecuritiesIndustryMember_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_AutomotiveMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_BusinessServicesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_ChemicalsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_CommunicationsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_EducationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="us-gaap_FinancialServicesSectorMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="us-gaap_HealthcareSectorMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_HotelGamingAndLeisureMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_HumanResourceSupportServicesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_InsuranceMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_InternetServicesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_ManufacturingMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_MarketingServicesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_OfficeProductsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_OilGasAndConsumableFuelsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_OtherMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_RetailAndConsumerProductsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquitySecuritiesIndustryMember" xlink:to="tslx_TransportationMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_US" xlink:label="country_US"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MidwestMember" xlink:label="tslx_MidwestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_AU" xlink:label="country_AU"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NortheastMember" xlink:label="tslx_NortheastMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_CA" xlink:label="country_CA"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SouthMember" xlink:label="tslx_SouthMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_FI" xlink:label="country_FI"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_WestMember" xlink:label="tslx_WestMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_DE" xlink:label="country_DE"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_LU" xlink:label="country_LU"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_NL" xlink:label="country_NL"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_NO" xlink:label="country_NO"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_SE" xlink:label="country_SE"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_GB" xlink:label="country_GB"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="srt_StatementGeographicalAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="tslx_PercentageOfInvestmentsAtFairValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_US" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="country_US" xlink:to="tslx_MidwestMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_AU" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="country_US" xlink:to="tslx_NortheastMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_CA" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="country_US" xlink:to="tslx_SouthMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_FI" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="country_US" xlink:to="tslx_WestMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_DE" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_LU" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_NL" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_NO" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_SE" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_GB" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureInvestmentsAtFairValueSummaryOfGeographicCompositionOfInvestmentsAtFairValueParentheticalDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfInvestmentsAtFairValue" xlink:label="tslx_PercentageOfInvestmentsAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2023/country-2023.xsd#country_FI" xlink:label="country_FI"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="us-gaap_DebtSecuritiesAvailableForSaleTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_SegmentGeographicalDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="srt_StatementGeographicalAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:to="tslx_PercentageOfInvestmentsAtFairValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_SegmentGeographicalDomain" xlink:to="country_FI" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems" xlink:label="us-gaap_DerivativeLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable" xlink:label="us-gaap_DerivativeTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapOneMember" xlink:label="tslx_InterestRateSwapOneMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTwoMember" xlink:label="tslx_InterestRateSwapTwoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DerivativeNotionalAmountHeldDuringPeriod" xlink:label="tslx_DerivativeNotionalAmountHeldDuringPeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapThreeMember" xlink:label="tslx_InterestRateSwapThreeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapFourMember" xlink:label="tslx_InterestRateSwapFourMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapFiveMember" xlink:label="tslx_InterestRateSwapFiveMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapSixMember" xlink:label="tslx_InterestRateSwapSixMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapSevenMember" xlink:label="tslx_InterestRateSwapSevenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapEightMember" xlink:label="tslx_InterestRateSwapEightMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapNineMember" xlink:label="tslx_InterestRateSwapNineMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTenMember" xlink:label="tslx_InterestRateSwapTenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapElevenMember" xlink:label="tslx_InterestRateSwapElevenMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapTwelveMember" xlink:label="tslx_InterestRateSwapTwelveMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwapThirteenMember" xlink:label="tslx_InterestRateSwapThirteenMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapOneMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeMaturityDates" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeInstrumentRiskAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapTwoMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="tslx_DerivativeNotionalAmountHeldDuringPeriod" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapThreeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_PaymentsForHedgeInvestingActivities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapFourMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_ProceedsFromHedgeInvestingActivities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapFiveMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapSixMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapSevenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapEightMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapNineMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapTenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapElevenMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapTwelveMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="tslx_InterestRateSwapThirteenMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeLineItems" xlink:label="us-gaap_DerivativeLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeTable" xlink:label="us-gaap_DerivativeTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="us-gaap_DerivativeContractTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestRateSwapMember" xlink:label="us-gaap_InterestRateSwapMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="us-gaap_DerivativeInstrumentRiskAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationDomain" xlink:label="us-gaap_HedgingDesignationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NondesignatedMember" xlink:label="us-gaap_NondesignatedMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain" xlink:label="us-gaap_PledgedStatusDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetPledgedAsCollateralMember" xlink:label="us-gaap_AssetPledgedAsCollateralMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseMember" xlink:label="us-gaap_InterestExpenseMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusAxis" xlink:label="us-gaap_PledgedStatusAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PledgedStatusDomain" xlink:label="us-gaap_PledgedStatusDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_HedgingDesignationAxis" xlink:label="us-gaap_HedgingDesignationAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignExchangeForwardMember" xlink:label="us-gaap_ForeignExchangeForwardMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DesignatedAsHedgingInstrumentMember" xlink:label="us-gaap_DesignatedAsHedgingInstrumentMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueOfDerivativeNet" xlink:label="us-gaap_DerivativeFairValueOfDerivativeNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Cash" xlink:label="us-gaap_Cash"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_InterestRateSwapMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DerivativeInstrumentRiskAxis" xlink:to="us-gaap_DerivativeContractTypeDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_NondesignatedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_PledgedStatusDomain" xlink:to="us-gaap_AssetPledgedAsCollateralMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DerivativeInstrumentRiskAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_InterestExpenseMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_PledgedStatusAxis" xlink:to="us-gaap_PledgedStatusDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_PledgedStatusAxis" xlink:to="us-gaap_PledgedStatusDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_HedgingDesignationAxis" xlink:to="us-gaap_HedgingDesignationDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeContractTypeDomain" xlink:to="us-gaap_ForeignExchangeForwardMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_HedgingDesignationDomain" xlink:to="us-gaap_DesignatedAsHedgingInstrumentMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_HedgingDesignationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_DerivativeFairValueOfDerivativeNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_IncomeStatementLocationAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DerivativeLineItems" xlink:to="us-gaap_Cash" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DerivativeTable" xlink:to="us-gaap_PledgedStatusAxis" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradingSecuritiesDebt" xlink:label="us-gaap_TradingSecuritiesDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="us-gaap_FairValueInputsLevel1Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestments" xlink:label="tslx_EquityAndOtherInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="us-gaap_FairValueInputsLevel2Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestments" xlink:label="tslx_StructuredCreditInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="us-gaap_InvestmentsFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwaps" xlink:label="tslx_InterestRateSwaps"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsFairValueDisclosureNet" xlink:label="tslx_InvestmentsFairValueDisclosureNet"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_TradingSecuritiesDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel1Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_EquityAndOtherInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel2Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_StructuredCreditInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_InvestmentsFairValueDisclosure" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_InterestRateSwaps" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="tslx_InvestmentsFairValueDisclosureNet" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsChangesInFairValueOfInvestmentsUsingLevel3InputsDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList" xlink:label="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList" xlink:label="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" xlink:label="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet" xlink:label="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetValue" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPurchases" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSettlements" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetSales" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetsMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueAssetRecurringBasisStillHeldUnrealizedGainLossStatementOfIncomeExtensibleList" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetGainLossIncludedInEarnings1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueRecurringBasisUnobservableInputReconciliationAssetGainLossStatementOfIncomeExtensibleList" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:to="us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersNet" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsNetChangeInUnrealizedGainsOrLossesOnInvestmentsForWhichLevel3InputsWereUsedInDeterminingFairValueDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" xlink:label="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:to="us-gaap_DebtAndEquitySecuritiesUnrealizedGainLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestment" xlink:label="us-gaap_AlternativeInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueAxis" xlink:label="us-gaap_ValuationTechniqueAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputDiscountRateMember" xlink:label="us-gaap_MeasurementInputDiscountRateMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="us-gaap_ValuationTechniqueDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeApproachValuationTechniqueMember" xlink:label="us-gaap_IncomeApproachValuationTechniqueMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="us-gaap_MeasurementInputTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="us-gaap_ValuationTechniqueDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AlternativeInvestmentMeasurementInput" xlink:label="us-gaap_AlternativeInvestmentMeasurementInput"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MeasurementInputComparabilityAdjustmentMember" xlink:label="us-gaap_MeasurementInputComparabilityAdjustmentMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_MarketApproachValuationTechniqueMember" xlink:label="us-gaap_MarketApproachValuationTechniqueMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_WeightedAverageMember" xlink:label="srt_WeightedAverageMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_AlternativeInvestment" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_ValuationTechniqueAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputDiscountRateMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_IncomeApproachValuationTechniqueMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_MeasurementInputTypeAxis" xlink:to="us-gaap_MeasurementInputTypeDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_MeasurementInputTypeAxis" xlink:to="us-gaap_MeasurementInputTypeDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ValuationTechniqueAxis" xlink:to="us-gaap_ValuationTechniqueDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_ValuationTechniqueAxis" xlink:to="us-gaap_ValuationTechniqueDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_AlternativeInvestmentMeasurementInput" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputComparabilityAdjustmentMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_MarketApproachValuationTechniqueMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_MeasurementInputTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_WeightedAverageMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfLevel3InvestmentsAtFairValueAndSignificantUnobservableInputsUsedInValuationsParenthe">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradingSecuritiesDebt" xlink:label="us-gaap_TradingSecuritiesDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueAxis" xlink:label="us-gaap_ValuationTechniqueAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDomain" xlink:label="us-gaap_ValuationTechniqueDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AssetValuationWaterfallMember" xlink:label="tslx_AssetValuationWaterfallMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="us-gaap_InvestmentTypeCategorizationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FirstLienDebtInvestmentsMember" xlink:label="tslx_FirstLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" xlink:label="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BlackScholesModelMember" xlink:label="tslx_BlackScholesModelMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SecondLienDebtInvestmentsMember" xlink:label="tslx_SecondLienDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CostModelMember" xlink:label="tslx_CostModelMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MezzanineDebtInvestmentsMember" xlink:label="tslx_MezzanineDebtInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ValuationTechniqueDiscountedCashFlowMember" xlink:label="us-gaap_ValuationTechniqueDiscountedCashFlowMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestmentsMember" xlink:label="tslx_EquityAndOtherInvestmentsMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ValuationTechniqueCostOfInvestmentsMember" xlink:label="tslx_ValuationTechniqueCostOfInvestmentsMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_TradingSecuritiesDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_ValuationTechniqueAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_AssetValuationWaterfallMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueInputsLevel3Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeCategorizationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_FirstLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_ValuationTechniqueAxis" xlink:to="us-gaap_ValuationTechniqueDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:to="us-gaap_EquitySecuritiesFvNiCurrentAndNoncurrent" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_InvestmentTypeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_BlackScholesModelMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_SecondLienDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_CostModelMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_MezzanineDebtInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="us-gaap_ValuationTechniqueDiscountedCashFlowMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_InvestmentTypeCategorizationMember" xlink:to="tslx_EquityAndOtherInvestmentsMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ValuationTechniqueDomain" xlink:to="tslx_ValuationTechniqueCostOfInvestmentsMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsFairValueOfNotesDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:label="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:label="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayable" xlink:label="us-gaap_NotesPayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NotesPayableFairValueDisclosure" xlink:label="us-gaap_NotesPayableFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:to="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:to="us-gaap_NotesPayable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_FairValueDisclosureOfAssetAndLiabilityNotMeasuredAtFairValueTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FairValueDisclosureAssetAndLiabilityNotMeasuredAtFairValueLineItems" xlink:to="us-gaap_NotesPayableFairValueDisclosure" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ObligorGroupMember" xlink:label="srt_ObligorGroupMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AssetCoveragePercentage" xlink:label="tslx_AssetCoveragePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ThreeMonthLiborMember" xlink:label="tslx_ThreeMonthLiborMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_VariableRateDomain" xlink:label="us-gaap_VariableRateDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="srt_ConsolidatedEntitiesAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnApril232027Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril232027Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_BaseRateMember" xlink:label="us-gaap_BaseRateMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityCommitmentFeeAmount" xlink:label="us-gaap_LineOfCreditFacilityCommitmentFeeAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember" xlink:label="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolvingCreditFacilityMaturityOnApril242029Member" xlink:label="tslx_RevolvingCreditFacilityMaturityOnApril242029Member"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LineOfCreditFacilityExtendedDate" xlink:label="tslx_LineOfCreditFacilityExtendedDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LetterOfCreditMember" xlink:label="us-gaap_LetterOfCreditMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LineOfCreditFacilityStatedMaturityDate" xlink:label="tslx_LineOfCreditFacilityStatedMaturityDate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="us-gaap_LineOfCreditFacilityExpirationDate1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCredit" xlink:label="us-gaap_LineOfCredit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="us-gaap_LettersOfCreditOutstandingAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" xlink:label="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" xlink:label="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" xlink:label="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RatioOfIndebtednessToNetCapital1" xlink:label="us-gaap_RatioOfIndebtednessToNetCapital1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" xlink:label="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AdditionalAggregatePrincipalAmount" xlink:label="tslx_AdditionalAggregatePrincipalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="us-gaap_DebtInstrumentMaturityDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeMaturityDates" xlink:label="us-gaap_DerivativeMaturityDates"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ExtinguishmentOfDebtAmount" xlink:label="us-gaap_ExtinguishmentOfDebtAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentAmount1" xlink:label="us-gaap_DebtConversionConvertedInstrumentAmount1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DebtConversionPrincipalAmount" xlink:label="tslx_DebtConversionPrincipalAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:label="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" xlink:label="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromUnsecuredNotesPayable" xlink:label="us-gaap_ProceedsFromUnsecuredNotesPayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" xlink:label="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" xlink:label="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="us-gaap_DerivativeNotionalAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="srt_ObligorGroupMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_AssetCoveragePercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableRateDomain" xlink:to="tslx_ThreeMonthLiborMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnApril232027Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_BaseRateMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityCommitmentFeeAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_VariableRateDomain" xlink:to="us-gaap_SecuredOvernightFinancingRateSofrOvernightIndexSwapRateMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_VariableRateAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="srt_ConsolidatedEntitiesAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_GainsLossesOnExtinguishmentOfDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="tslx_RevolvingCreditFacilityMaturityOnApril242029Member" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_LineOfCreditFacilityExtendedDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_LetterOfCreditMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_LineOfCreditFacilityStatedMaturityDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityExpirationDate1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCredit" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LettersOfCreditOutstandingAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityInterestRateDuringPeriod" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityInterestRateAtPeriodEnd" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityUnusedCapacityCommitmentFeePercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_RatioOfIndebtednessToNetCapital1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_StockholdersEquity" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_AdditionalAggregatePrincipalAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="19" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentMaturityDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="20" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeMaturityDates" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="21" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentConvertibleConversionPrice1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="22" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_ExtinguishmentOfDebtAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="23" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtConversionConvertedInstrumentAmount1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="24" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtConversionConvertedInstrumentSharesIssued1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="25" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_DebtConversionPrincipalAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="26" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="27" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="28" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_ProceedsFromUnsecuredNotesPayable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="29" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentDescriptionOfVariableRateBasis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="30" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="31" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="32" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeNotionalAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="33" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SwapSettlement" xlink:label="tslx_SwapSettlement"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestAndDebtExpense" xlink:label="us-gaap_InterestAndDebtExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityAverageOutstandingAmount" xlink:label="us-gaap_LineOfCreditFacilityAverageOutstandingAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebtWeightedAverageInterestRateOverTime" xlink:label="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_InterestExpenseDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_AmortizationOfFinancingCosts" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_SwapSettlement" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_InterestAndDebtExpense" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityAverageOutstandingAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LongTermDebtWeightedAverageInterestRateOverTime" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OriginalIssueDiscountNetOfAccretion" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfAnEffectiveHedge" xlink:label="tslx_FairValueOfAnEffectiveHedge"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentCarryingAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_OriginalIssueDiscountNetOfAccretion" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DeferredFinanceCostsNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="tslx_FairValueOfAnEffectiveHedge" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LongTermDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfDebtObligationsDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentFaceAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentCarryingAmount" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_LongTermDebt" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfDebtObligationsParentheticalDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="us-gaap_DebtInstrumentLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentTable" xlink:label="us-gaap_DebtInstrumentTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityAxis" xlink:label="us-gaap_CreditFacilityAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyThreeNotesMember" xlink:label="tslx_TwoThousandTwentyThreeNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CreditFacilityDomain" xlink:label="us-gaap_CreditFacilityDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="us-gaap_RevolvingCreditFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" xlink:label="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyFourNotesMember" xlink:label="tslx_TwoThousandTwentyFourNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" xlink:label="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentySixNotesMember" xlink:label="tslx_TwoThousandTwentySixNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" xlink:label="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyEightNotesMember" xlink:label="tslx_TwoThousandTwentyEightNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyNineNotesMember" xlink:label="tslx_TwoThousandTwentyNineNotesMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_CreditFacilityAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyThreeNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_CreditFacilityDomain" xlink:to="us-gaap_RevolvingCreditFacilityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_CreditFacilityAxis" xlink:to="us-gaap_CreditFacilityDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyFourNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DebtInstrumentIncreaseDecreaseForPeriodNet" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DebtInstrumentTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentySixNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentLineItems" xlink:to="us-gaap_DerivativeFairValueHedgeIncludedInEffectivenessGainLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyEightNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyNineNotesMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AlaskaBidcoOyMember" xlink:label="tslx_AlaskaBidcoOyMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawMember" xlink:label="tslx_DelayedDrawMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="srt_ConsolidatedEntitiesAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PurchaseCommitmentToFundInvestment" xlink:label="tslx_PurchaseCommitmentToFundInvestment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="us-gaap_FinancialInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AlphaMidcoIncMember" xlink:label="tslx_AlphaMidcoIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverMember" xlink:label="tslx_RevolverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AmericanAchievementCorpMember" xlink:label="tslx_AmericanAchievementCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawAndRevolverMember" xlink:label="tslx_DelayedDrawAndRevolverMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ApteanIncMember" xlink:label="tslx_ApteanIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawAndMembershipInterestMember" xlink:label="tslx_DelayedDrawAndMembershipInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ArrowbuyerIncMember" xlink:label="tslx_ArrowbuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverAndPartnershipInterestMember" xlink:label="tslx_RevolverAndPartnershipInterestMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ArtisanBidcoIncMember" xlink:label="tslx_ArtisanBidcoIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RevolverEquityMember" xlink:label="tslx_RevolverEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AsgIiLlcMember" xlink:label="tslx_AsgIiLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawEquityMember" xlink:label="tslx_DelayedDrawEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AvalaraIncMember" xlink:label="tslx_AvalaraIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawRevolverPreferredEquityMember" xlink:label="tslx_DelayedDrawRevolverPreferredEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AxonifyIncMember" xlink:label="tslx_AxonifyIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DelayedDrawRevolverEquityMember" xlink:label="tslx_DelayedDrawRevolverEquityMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_AzuriteIntermediateHoldingsIncMember" xlink:label="tslx_AzuriteIntermediateHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BabylonFincoLimitedMember" xlink:label="tslx_BabylonFincoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BanyanSoftwareHoldingsLlcMember" xlink:label="tslx_BanyanSoftwareHoldingsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BayshoreIntermediate2LPMember" xlink:label="tslx_BayshoreIntermediate2LPMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BCTOAcePurchaserIncMember" xlink:label="tslx_BCTOAcePurchaserIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BctoBluebillBuyerIncMember" xlink:label="tslx_BctoBluebillBuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BearOpCoLLCMember" xlink:label="tslx_BearOpCoLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BenNevisMidcoLimitedMember" xlink:label="tslx_BenNevisMidcoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BlueSnapIncMember" xlink:label="tslx_BlueSnapIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BtrsHoldingIncMember" xlink:label="tslx_BtrsHoldingIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CordanceOperationsLlcMember" xlink:label="tslx_CordanceOperationsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CoupaHoldingsLLCMember" xlink:label="tslx_CoupaHoldingsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CrewlineBuyerIncMember" xlink:label="tslx_CrewlineBuyerIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DiscoParentIncMember" xlink:label="tslx_DiscoParentIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DyeDurhamCorpMember" xlink:label="tslx_DyeDurhamCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EDBParentLLCMember" xlink:label="tslx_EDBParentLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EdgeBidcoBVMember" xlink:label="tslx_EdgeBidcoBVMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ElysianFincoLtdMember" xlink:label="tslx_ElysianFincoLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EmploymentHeroHoldingsPtyLtdMember" xlink:label="tslx_EmploymentHeroHoldingsPtyLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EMSLinqIncMember" xlink:label="tslx_EMSLinqIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ErlingLuxBidcoSarlMember" xlink:label="tslx_ErlingLuxBidcoSarlMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ExtraHopNetworksIncMember" xlink:label="tslx_ExtraHopNetworksIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FullsteamOperationsLlcMember" xlink:label="tslx_FullsteamOperationsLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ForeScoutTechnologiesIncMember" xlink:label="tslx_ForeScoutTechnologiesIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_GalileoParentincMember" xlink:label="tslx_GalileoParentincMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HeritageEnvironmentalServicesIncMember" xlink:label="tslx_HeritageEnvironmentalServicesIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HippoXpaBidcoAbMember" xlink:label="tslx_HippoXpaBidcoAbMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HirevueIncMember" xlink:label="tslx_HirevueIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_HornetsecurityHoldingGmbhMember" xlink:label="tslx_HornetsecurityHoldingGmbhMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IbisIntermediateCoMember" xlink:label="tslx_IbisIntermediateCoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IRGSEHoldingCorpMember" xlink:label="tslx_IRGSEHoldingCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_KangarooBidcoASMember" xlink:label="tslx_KangarooBidcoASMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_KyribaCorpMember" xlink:label="tslx_KyribaCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LaramieEnergyLLCMember" xlink:label="tslx_LaramieEnergyLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LeantaasHoldingsIncMember" xlink:label="tslx_LeantaasHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LucidworksIncMember" xlink:label="tslx_LucidworksIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_MarcuraEquitiesLtdMember" xlink:label="tslx_MarcuraEquitiesLtdMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetwrixCorpMember" xlink:label="tslx_NetwrixCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OutsystemsLuxcoMember" xlink:label="tslx_OutsystemsLuxcoMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PassportLabsIncMember" xlink:label="tslx_PassportLabsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PdiTaHoldingsIncMember" xlink:label="tslx_PdiTaHoldingsIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PingIdentityCorporationMember" xlink:label="tslx_PingIdentityCorporationMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PrimeRevenueIncMember" xlink:label="tslx_PrimeRevenueIncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_Project44IncMember" xlink:label="tslx_Project44IncMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RapidDataGmbhUnternehmensberatungMember" xlink:label="tslx_RapidDataGmbhUnternehmensberatungMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ReliaQuestHoldingsLLCMember" xlink:label="tslx_ReliaQuestHoldingsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SkylarkUkDebtcoLimitedMember" xlink:label="tslx_SkylarkUkDebtcoLimitedMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SlBuyerCorpMember" xlink:label="tslx_SlBuyerCorpMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TangoManagementConsultingLLCMember" xlink:label="tslx_TangoManagementConsultingLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TRPAssetsLLCMember" xlink:label="tslx_TRPAssetsLLCMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TruckLiteCoLlcMember" xlink:label="tslx_TruckLiteCoLlcMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_WranglerTopcoLlcMember" xlink:label="tslx_WranglerTopcoLlcMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_LossContingenciesTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AlaskaBidcoOyMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_LossContingenciesTable" xlink:to="srt_ConsolidatedEntitiesAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="tslx_PurchaseCommitmentToFundInvestment" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FinancialInstrumentAxis" xlink:to="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_ConsolidatedEntitiesAxis" xlink:to="srt_ConsolidatedEntitiesDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AlphaMidcoIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_RevolverMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_FinancialInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AmericanAchievementCorpMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawAndRevolverMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ApteanIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawAndMembershipInterestMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ArrowbuyerIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_RevolverAndPartnershipInterestMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ArtisanBidcoIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_RevolverEquityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AsgIiLlcMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawEquityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AvalaraIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawRevolverPreferredEquityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AxonifyIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:to="tslx_DelayedDrawRevolverEquityMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_AzuriteIntermediateHoldingsIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BabylonFincoLimitedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BanyanSoftwareHoldingsLlcMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BayshoreIntermediate2LPMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="13" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BCTOAcePurchaserIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="14" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BctoBluebillBuyerIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="15" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BearOpCoLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="16" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BenNevisMidcoLimitedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="17" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BlueSnapIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="18" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_BtrsHoldingIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="19" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_CordanceOperationsLlcMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="20" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_CoupaHoldingsLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="21" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_CrewlineBuyerIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="22" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_DiscoParentIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="23" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_DyeDurhamCorpMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="24" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EDBParentLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="25" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EdgeBidcoBVMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="26" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ElysianFincoLtdMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="27" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EmploymentHeroHoldingsPtyLtdMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="28" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_EMSLinqIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="29" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ErlingLuxBidcoSarlMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="30" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ExtraHopNetworksIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="31" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_FullsteamOperationsLlcMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="32" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ForeScoutTechnologiesIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="33" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_GalileoParentincMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="34" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HeritageEnvironmentalServicesIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="35" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HippoXpaBidcoAbMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="36" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HirevueIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="37" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_HornetsecurityHoldingGmbhMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="38" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_IbisIntermediateCoMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="39" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_IRGSEHoldingCorpMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="40" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_KangarooBidcoASMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="41" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_KyribaCorpMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="42" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_LaramieEnergyLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="43" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_LeantaasHoldingsIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="44" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_LucidworksIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="45" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_MarcuraEquitiesLtdMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="46" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_NetwrixCorpMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="47" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_OutsystemsLuxcoMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="48" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PassportLabsIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="49" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PdiTaHoldingsIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="50" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PingIdentityCorporationMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="51" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_PrimeRevenueIncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="52" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_Project44IncMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="53" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_RapidDataGmbhUnternehmensberatungMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="54" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_ReliaQuestHoldingsLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="55" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_SkylarkUkDebtcoLimitedMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="56" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_SlBuyerCorpMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="57" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_TangoManagementConsultingLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="58" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_TRPAssetsLLCMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="59" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_TruckLiteCoLlcMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="60" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="tslx_WranglerTopcoLlcMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesLineItems" xlink:label="us-gaap_LossContingenciesLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LossContingenciesTable" xlink:label="us-gaap_LossContingenciesTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherCommitment" xlink:label="us-gaap_OtherCommitment"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:label="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnfundedLoanCommitmentMember" xlink:label="us-gaap_UnfundedLoanCommitmentMember"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_LossContingenciesTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_LossContingenciesTable" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_LossContingenciesLineItems" xlink:to="us-gaap_OtherCommitment" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis" xlink:to="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_FinancingReceivableRecordedInvestmentClassOfFinancingReceivableDomain" xlink:to="us-gaap_UnfundedLoanCommitmentMember" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems" xlink:label="us-gaap_ClassOfStockLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="us-gaap_ScheduleOfStockByClassTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="us-gaap_OverAllotmentOptionMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtConversionOriginalDebtAmount1" xlink:label="us-gaap_DebtConversionOriginalDebtAmount1"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_CurrentMarketPricePerSharePercentage" xlink:label="tslx_CurrentMarketPricePerSharePercentage"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramPeriodInForce1" xlink:label="us-gaap_StockRepurchaseProgramPeriodInForce1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockRepurchaseProgramExpirationDate" xlink:label="us-gaap_StockRepurchaseProgramExpirationDate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="us-gaap_TreasuryStockSharesAcquired"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:label="us-gaap_TreasuryStockAcquiredAverageCostPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="us-gaap_TreasuryStockValueAcquiredCostMethod"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_ScheduleOfStockByClassTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_CommonStockSharesIssued" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_CommonStockMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_StatementEquityComponentsAxis" xlink:to="us-gaap_EquityComponentDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_OverAllotmentOptionMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_StatementEquityComponentsAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_SharesIssuedPricePerShare" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_SubsidiarySaleOfStockAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_DebtConversionOriginalDebtAmount1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="tslx_CurrentMarketPricePerSharePercentage" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockRepurchaseProgramAuthorizedAmount1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockRepurchaseProgramPeriodInForce1" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockRepurchaseProgramExpirationDate" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_TreasuryStockSharesAcquired" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_TreasuryStockAcquiredAverageCostPerShare" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="12" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_TreasuryStockValueAcquiredCostMethod" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureNetAssetsScheduleOfSharesIssuedToStockholdersDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ClassOfStockLineItems" xlink:label="us-gaap_ClassOfStockLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="us-gaap_ScheduleOfStockByClassTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAxis" xlink:label="us-gaap_DividendsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDomain" xlink:label="us-gaap_DividendsDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDomain" xlink:label="us-gaap_DividendsDomain_default"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BaseDividendMember" xlink:label="tslx_BaseDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SupplementalDividendMember" xlink:label="tslx_SupplementalDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" xlink:label="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" xlink:label="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_ScheduleOfStockByClassTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_ScheduleOfStockByClassTable" xlink:to="us-gaap_DividendsAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DividendsAxis" xlink:to="us-gaap_DividendsDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="us-gaap_DividendsAxis" xlink:to="us-gaap_DividendsDomain_default" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_BaseDividendMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_SupplementalDividendMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_ClassOfStockLineItems" xlink:to="us-gaap_StockIssuedDuringPeriodSharesDividendReinvestmentPlan" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureEarningsPerShareComputationOfBasicAndDilutedEarningsPerCommonShareDetails">
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:label="tslx_EarningsPerShareBasicAndDilutedLineItems"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:label="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasicAbstract" xlink:label="us-gaap_EarningsPerShareBasicAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TwoThousandTwentyTwoConvertibleNotesMember" xlink:label="tslx_TwoThousandTwentyTwoConvertibleNotesMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareBasic" xlink:label="us-gaap_EarningsPerShareBasic"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:to="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="tslx_EarningsPerShareBasicAndDilutedLineItems" xlink:to="us-gaap_EarningsPerShareBasicAbstract" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="tslx_TwoThousandTwentyTwoConvertibleNotesMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_ProfitLoss" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentNameDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" xlink:to="us-gaap_DebtInstrumentAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_EarningsPerShareBasic" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_EarningsPerShareBasicAbstract" xlink:to="us-gaap_EarningsPerShareDiluted" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDividendsSummaryOfDividendsDeclaredDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableLineItems" xlink:label="us-gaap_DividendsPayableLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableTable" xlink:label="us-gaap_DividendsPayableTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsAxis" xlink:label="us-gaap_DividendsAxis"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsDomain" xlink:label="us-gaap_DividendsDomain"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SupplementalDividendMember" xlink:label="tslx_SupplementalDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_BaseDividendMember" xlink:label="tslx_BaseDividendMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableNature" xlink:label="us-gaap_DividendsPayableNature"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" xlink:label="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendPayableDateToBePaidDayMonthAndYear" xlink:label="us-gaap_DividendPayableDateToBePaidDayMonthAndYear"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DividendsPayableAmountPerShare" xlink:label="us-gaap_DividendsPayableAmountPerShare"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="us-gaap_DividendsAxis" xlink:to="us-gaap_DividendsDomain" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_SupplementalDividendMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableDateDeclaredDayMonthAndYear" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_DividendsPayableTable" xlink:to="us-gaap_DividendsAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsDomain" xlink:to="tslx_BaseDividendMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableNature" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableDateOfRecordDayMonthAndYear" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendPayableDateToBePaidDayMonthAndYear" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_DividendsPayableLineItems" xlink:to="us-gaap_DividendsPayableAmountPerShare" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesAdditionalInformationDetails">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardLineItems" xlink:label="us-gaap_TaxCreditCarryforwardLineItems"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TaxCreditCarryforwardTable" xlink:label="us-gaap_TaxCreditCarryforwardTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeMember" xlink:label="srt_RangeMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInDistributableEarnings" xlink:label="tslx_IncreaseDecreaseInDistributableEarnings"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInAdditionalPaidInCapital" xlink:label="tslx_IncreaseDecreaseInAdditionalPaidInCapital"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" xlink:label="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CurrentIncomeTaxExpenseBenefit" xlink:label="us-gaap_CurrentIncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NumberOfInvestments" xlink:label="tslx_NumberOfInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredTaxAssetsGross" xlink:label="us-gaap_DeferredTaxAssetsGross"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" xlink:label="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxCostOfInvestments" xlink:label="tslx_TaxCostOfInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" xlink:label="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" xlink:label="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpenseForFederalExciseTax" xlink:label="tslx_NetExpenseForFederalExciseTax"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_TaxCreditCarryforwardTable" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MinimumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="srt_RangeAxis" xlink:to="srt_RangeMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_IncreaseDecreaseInDistributableEarnings" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="us-gaap_TaxCreditCarryforwardTable" xlink:to="srt_RangeAxis" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="srt_RangeMember" xlink:to="srt_MaximumMember" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="1" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_IncreaseDecreaseInAdditionalPaidInCapital" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="3" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_CurrentIncomeTaxExpenseBenefit" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="4" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_DeferredIncomeTaxExpenseBenefit" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="5" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_NumberOfInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="6" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="us-gaap_DeferredTaxAssetsGross" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="7" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="8" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_TaxCostOfInvestments" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="9" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="10" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="11" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_TaxCreditCarryforwardLineItems" xlink:to="tslx_NetExpenseForFederalExciseTax" priority="2" use="optional"/>
        </link:definitionLink>
        <link:definitionLink xlink:type="extended" xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:definitionArc xlink:type="arc" order="0" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" priority="2" use="optional"/>
          <link:definitionArc xlink:type="arc" order="2" xbrldt:closed="false" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" priority="2" use="optional"/>
        </link:definitionLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedBalanceSheetsUnaudited">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_Liabilities" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_InvestmentOwnedAtFairValue" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AssetsNet" xlink:to="us-gaap_PreferredStockValue" order="0" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_LongTermDebt" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_CommitmentsAndContingencies" order="1" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue" order="1" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AssetsNet" xlink:to="us-gaap_CommonStockValue" order="1" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_ManagementFeePayable" order="1" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_AssetsNet" order="2" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_InterestReceivable" order="2" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AssetsNet" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock" order="2" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" order="2" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Assets" xlink:to="us-gaap_PrepaidExpenseAndOtherAssets" order="3" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AssetsNet" xlink:to="us-gaap_TreasuryStockValue" order="3" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" order="3" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_AssetsNet" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit" order="4" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="tslx_OtherPayablesToAffiliate" order="5" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_OtherLiabilities" order="7" weight="1.00" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentOwnedAtFairValue" xlink:label="us-gaap_InvestmentOwnedAtFairValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AssetsNet" xlink:label="us-gaap_AssetsNet"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeePayable" xlink:label="us-gaap_ManagementFeePayable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestReceivable" xlink:label="us-gaap_InterestReceivable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PrepaidExpenseAndOtherAssets" xlink:label="us-gaap_PrepaidExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherPayablesToAffiliate" xlink:label="tslx_OtherPayablesToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherLiabilities" xlink:label="us-gaap_OtherLiabilities"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_StatementConsolidatedStatementsOfOperationsUnaudited">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="us-gaap_GainLossOnSaleOfDerivatives" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="us-gaap_NonoperatingIncomeExpense" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentIncomeNet" xlink:to="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetExpense" xlink:to="us-gaap_OperatingExpenses" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="tslx_IncentiveFeesOnNetInvestmentIncome" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_InvestmentIncomeNet" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_InvestmentIncomeDividend" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossRealized" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:to="tslx_NetExpense" order="1" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentIncomeNet" xlink:to="us-gaap_IncomeTaxExpenseBenefit" order="1" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="us-gaap_UnrealizedGainLossOnInvestments" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="tslx_IncentiveFeesOnNetCapitalGains" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_ProfitLoss" xlink:to="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_InvestmentIncomeInterest" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:to="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="us-gaap_RealizedInvestmentGainsLosses" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetExpense" xlink:to="tslx_ManagementAndIncentiveFeeWaived" order="2" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_InterestExpense" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="tslx_PaidInKindInterestIncome" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:to="tslx_UnrealizedGainsLossesOnIncomeTaxProvision" order="3" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_NoninterestExpenseDirectorsFees" order="3" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OtherGeneralAndAdministrativeExpense" order="4" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_ProfessionalFees" order="5" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_OtherNonoperatingIncome" order="5" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_ManagementFeeExpense" order="6" weight="1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfDerivatives" xlink:label="us-gaap_GainLossOnSaleOfDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeNet" xlink:label="us-gaap_InvestmentIncomeNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetExpense" xlink:label="tslx_NetExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetInvestmentIncome" xlink:label="tslx_IncentiveFeesOnNetInvestmentIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeDividend" xlink:label="us-gaap_InvestmentIncomeDividend"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency" xlink:label="us-gaap_InvestmentCompanyRealizedAndUnrealizedGainLossOnInvestmentAndForeignCurrency"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossRealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="us-gaap_IncomeTaxExpenseBenefit"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnInvestments" xlink:label="us-gaap_UnrealizedGainLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncentiveFeesOnNetCapitalGains" xlink:label="tslx_IncentiveFeesOnNetCapitalGains"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentIncomeInterest" xlink:label="us-gaap_InvestmentIncomeInterest"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLosses" xlink:label="us-gaap_RealizedInvestmentGainsLosses"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ManagementAndIncentiveFeeWaived" xlink:label="tslx_ManagementAndIncentiveFeeWaived"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpense" xlink:label="us-gaap_InterestExpense"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PaidInKindInterestIncome" xlink:label="tslx_PaidInKindInterestIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UnrealizedGainsLossesOnIncomeTaxProvision" xlink:label="tslx_UnrealizedGainsLossesOnIncomeTaxProvision"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NoninterestExpenseDirectorsFees" xlink:label="us-gaap_NoninterestExpenseDirectorsFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherGeneralAndAdministrativeExpense" xlink:label="us-gaap_OtherGeneralAndAdministrativeExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfessionalFees" xlink:label="us-gaap_ProfessionalFees"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_OtherNonoperatingIncome" xlink:label="us-gaap_OtherNonoperatingIncome"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ManagementFeeExpense" xlink:label="us-gaap_ManagementFeeExpense"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/StatementConsolidatedStatementsOfCashFlowsUnaudited">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_ProfitLoss" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_ProceedsFromShortTermDebt" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_UnrealizedGainLossOnInvestments" order="1" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities" order="1" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_RepaymentsOfShortTermDebt" order="1" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_UnrealizedGainLossOnDerivatives" order="2" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_PaymentsOfFinancingCosts" order="2" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock" order="3" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_GainLossOnSaleOfDerivatives" order="4" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" order="5" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" order="6" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_RealizedInvestmentGainsLosses" order="8" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" order="11" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_AmortizationOfFinancingCosts" order="12" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_PaymentsOfDividends" order="12" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" order="13" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_PurchasesAndOriginationsOfInvestmentsNet" order="14" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_GainLossFormAdjustmentOfPaidInKindInterest" order="15" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_ProceedsFromInvestmentsNet" order="16" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_RepaymentsOnInvestments" order="17" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" order="19" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_IncreaseDecreaseInInterestReceivablePaidInKind" order="20" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" order="21" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" order="22" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" order="23" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" order="24" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent" order="25" weight="-1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" order="26" weight="1.00" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProfitLoss" xlink:label="us-gaap_ProfitLoss"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromShortTermDebt" xlink:label="us-gaap_ProceedsFromShortTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnInvestments" xlink:label="us-gaap_UnrealizedGainLossOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RepaymentsOfShortTermDebt" xlink:label="us-gaap_RepaymentsOfShortTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_UnrealizedGainLossOnDerivatives" xlink:label="us-gaap_UnrealizedGainLossOnDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfFinancingCosts" xlink:label="us-gaap_PaymentsOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_GainLossOnSaleOfDerivatives" xlink:label="us-gaap_GainLossOnSaleOfDerivatives"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" xlink:label="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_RealizedInvestmentGainsLosses" xlink:label="us-gaap_RealizedInvestmentGainsLosses"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments" xlink:label="us-gaap_AccretionAmortizationOfDiscountsAndPremiumsInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsOfDividends" xlink:label="us-gaap_PaymentsOfDividends"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_PurchasesAndOriginationsOfInvestmentsNet" xlink:label="tslx_PurchasesAndOriginationsOfInvestmentsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_GainLossFormAdjustmentOfPaidInKindInterest" xlink:label="tslx_GainLossFormAdjustmentOfPaidInKindInterest"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_ProceedsFromInvestmentsNet" xlink:label="tslx_ProceedsFromInvestmentsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_RepaymentsOnInvestments" xlink:label="tslx_RepaymentsOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet" xlink:label="us-gaap_IncreaseDecreaseInAccruedInterestReceivableNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInInterestReceivablePaidInKind" xlink:label="tslx_IncreaseDecreaseInInterestReceivablePaidInKind"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" xlink:label="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" xlink:label="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent" xlink:label="us-gaap_IncreaseDecreaseInDueFromAffiliatesCurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_IncreaseDecreaseInOtherOperatingLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingLiabilities"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDerivativesSummaryOfAmountsPaidAndReceivedOnInterestRateSwapTransactionsExcludingUpfrontFeesDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:to="us-gaap_PaymentsForHedgeInvestingActivities" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:to="us-gaap_ProceedsFromHedgeInvestingActivities" order="1" weight="-1.00" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_PaymentsForHedgeInvestingActivities" xlink:label="us-gaap_PaymentsForHedgeInvestingActivities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_ProceedsFromHedgeInvestingActivities" xlink:label="us-gaap_ProceedsFromHedgeInvestingActivities"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsFairValueMeasurementsOfInvestmentsDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentsFairValueDisclosure" xlink:to="us-gaap_TradingSecuritiesDebt" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_InvestmentsFairValueDisclosureNet" xlink:to="us-gaap_InvestmentsFairValueDisclosure" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentsFairValueDisclosure" xlink:to="tslx_EquityAndOtherInvestments" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_InvestmentsFairValueDisclosureNet" xlink:to="tslx_InterestRateSwaps" order="1" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentsFairValueDisclosure" xlink:to="tslx_StructuredCreditInvestments" order="2" weight="1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="us-gaap_InvestmentsFairValueDisclosure"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_TradingSecuritiesDebt" xlink:label="us-gaap_TradingSecuritiesDebt"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentsFairValueDisclosureNet" xlink:label="tslx_InvestmentsFairValueDisclosureNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_EquityAndOtherInvestments" xlink:label="tslx_EquityAndOtherInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InterestRateSwaps" xlink:label="tslx_InterestRateSwaps"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_StructuredCreditInvestments" xlink:label="tslx_StructuredCreditInvestments"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/Role_DisclosureDebtScheduleOfComponentsOfInterestExpenseDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="us-gaap_InterestExpenseDebt" order="0" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" order="2" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="us-gaap_AmortizationOfFinancingCosts" order="3" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium" order="4" weight="1.00" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="tslx_SwapSettlement" order="5" weight="-1.00" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestAndDebtExpense" xlink:label="us-gaap_InterestAndDebtExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts" xlink:label="us-gaap_DebtRelatedCommitmentFeesAndDebtIssuanceCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_SwapSettlement" xlink:label="tslx_SwapSettlement"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureDebtScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRatesDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LongTermDebt" xlink:to="us-gaap_DeferredFinanceCostsNet" order="0" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LongTermDebt" xlink:to="tslx_FairValueOfAnEffectiveHedge" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LongTermDebt" xlink:to="us-gaap_DebtInstrumentCarryingAmount" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_LongTermDebt" xlink:to="tslx_OriginalIssueDiscountNetOfAccretion" order="3" weight="1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_FairValueOfAnEffectiveHedge" xlink:label="tslx_FairValueOfAnEffectiveHedge"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OriginalIssueDiscountNetOfAccretion" xlink:label="tslx_OriginalIssueDiscountNetOfAccretion"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxCharacterOfShareholderDistributionsDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_DividendsDeclaredDuringThePeriod" xlink:to="tslx_OrdinaryIncome" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_DividendsDeclaredDuringThePeriod" xlink:to="tslx_LongTermCapitalGains" order="1" weight="1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredDuringThePeriod" xlink:label="tslx_DividendsDeclaredDuringThePeriod"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OrdinaryIncome" xlink:label="tslx_OrdinaryIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_LongTermCapitalGains" xlink:label="tslx_LongTermCapitalGains"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfTaxBasisComponentsOfDistributableEarningsDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DistributedEarnings" xlink:to="tslx_UndistributedNetInvestmentIncomeTaxBasis" order="0" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DistributedEarnings" xlink:to="tslx_UndistributedNetRealizedGainsTaxBasis" order="1" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DistributedEarnings" xlink:to="tslx_NetUnrealizedGainsOnInvestments" order="2" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_DistributedEarnings" xlink:to="tslx_OtherTemporaryDifferences" order="3" weight="1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_DistributedEarnings" xlink:label="us-gaap_DistributedEarnings"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UndistributedNetInvestmentIncomeTaxBasis" xlink:label="tslx_UndistributedNetInvestmentIncomeTaxBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_UndistributedNetRealizedGainsTaxBasis" xlink:label="tslx_UndistributedNetRealizedGainsTaxBasis"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetUnrealizedGainsOnInvestments" xlink:label="tslx_NetUnrealizedGainsOnInvestments"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherTemporaryDifferences" xlink:label="tslx_OtherTemporaryDifferences"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureIncomeTaxesSummaryOfReconciliationIncreaseInNetAssetsDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_TaxableIncome" xlink:to="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_TaxableIncome" xlink:to="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_TaxableIncome" xlink:to="tslx_OtherIncomeForTaxPurposesNotBook" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_TaxableIncome" xlink:to="tslx_DeferredOrganizationCosts" order="3" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_TaxableIncome" xlink:to="tslx_OtherExpensesNotCurrentlyDeductible" order="4" weight="-1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="tslx_TaxableIncome" xlink:to="tslx_OtherBookTaxDifferences" order="5" weight="-1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_TaxableIncome" xlink:label="tslx_TaxableIncome"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" xlink:label="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" xlink:label="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherIncomeForTaxPurposesNotBook" xlink:label="tslx_OtherIncomeForTaxPurposesNotBook"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DeferredOrganizationCosts" xlink:label="tslx_DeferredOrganizationCosts"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherExpensesNotCurrentlyDeductible" xlink:label="tslx_OtherExpensesNotCurrentlyDeductible"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_OtherBookTaxDifferences" xlink:label="tslx_OtherBookTaxDifferences"/>
        </link:calculationLink>
        <link:calculationLink xlink:type="extended" xlink:role="http://sixthstreetspecialtylending.com/20240331/taxonomy/role/DisclosureFinancialHighlightsSummaryOfFinancialHighlightsForOneShareCommonStockOutstandingDetails">
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:to="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" order="0" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:to="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" order="1" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="tslx_IssuanceOfCommonStockNetOfOfferingCosts" order="2" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" order="3" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" order="4" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="tslx_DividendDeclaredFromRealizedGainsPerShare" order="5" weight="1" use="optional"/>
          <link:calculationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/summation-item" xlink:from="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:to="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" order="8" weight="1" use="optional"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease" xlink:label="us-gaap_InvestmentCompanyNetAssetValuePerSharePeriodIncreaseDecrease"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossFromOperationsPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare" xlink:label="us-gaap_InvestmentCompanyInvestmentIncomeLossPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyDistributionToShareholdersPerShare" xlink:label="us-gaap_InvestmentCompanyDistributionToShareholdersPerShare"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd#us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare" xlink:label="us-gaap_InvestmentCompanyGainLossOnInvestmentPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_IssuanceOfCommonStockNetOfOfferingCosts" xlink:label="tslx_IssuanceOfCommonStockNetOfOfferingCosts"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" xlink:label="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" xlink:label="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendDeclaredFromRealizedGainsPerShare" xlink:label="tslx_DividendDeclaredFromRealizedGainsPerShare"/>
          <link:loc xlink:type="locator" xlink:href="tslx-20240331.xsd#tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" xlink:label="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare"/>
        </link:calculationLink>
      </link:linkbase>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:element id="tslx_MidwestMember" name="MidwestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" name="PercentageOfWeightedCumulativeRealizedCapitalGainsLessRealizedCapitalLossesAndUnrealizedCapitalLossesThroughMarch312014HurdleRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AvalaraIncMember" name="AvalaraIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OilGasAndConsumableFuelsMember" name="OilGasAndConsumableFuelsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DyeDurhamCorpMember" name="DyeDurhamCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" name="FutureRealizedCapitalGainsPriorToAprilFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" name="PercentageOfWeightedCumulativeRealizedCapitalGainsLessCumulativeRealizedCapitalLossesAndUnrealizedCapitalLosses" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SouthMember" name="SouthMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ThreeMonthLiborMember" name="ThreeMonthLiborMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" name="TwoThousandTwentyThreeTwentyFourTwentySixTwentyeightAndTwentyNineNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BtrsHoldingIncMember" name="BtrsHoldingIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BctoBluebillBuyerIncMember" name="BctoBluebillBuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NumberOfInvestments" name="NumberOfInvestments" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" name="TwoThousandTwentyThreeTwentyFourTwentySixAndTwentyEightNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyTwoConvertibleNotesMember" name="TwoThousandTwentyTwoConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RisksAssociatedWithConflictsOfInterestMember" name="RisksAssociatedWithConflictsOfInterestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DeferredOrganizationCosts" name="DeferredOrganizationCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_KangarooBidcoASMember" name="KangarooBidcoASMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherBookTaxDifferences" name="OtherBookTaxDifferences" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_PercentageOfManagementFeeCalculatedOnGrossAssets" name="PercentageOfManagementFeeCalculatedOnGrossAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ForeScoutTechnologiesIncMember" name="ForeScoutTechnologiesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UnrealizedGainOnInvestments" name="UnrealizedGainOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_DividendDeclaredFromRealizedGainsPerShare" name="DividendDeclaredFromRealizedGainsPerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_OtherIncomeForTaxPurposesNotBook" name="OtherIncomeForTaxPurposesNotBook" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_EarningsPerShareBasicAndDilutedLineItems" name="EarningsPerShareBasicAndDilutedLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncomeTaxesIncludingExciseTaxesPolicyTextBlock" name="IncomeTaxesIncludingExciseTaxesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock" name="SummaryOfTaxBasisComponentsOfDistributableEarningsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ErlingLuxBidcoSarlMember" name="ErlingLuxBidcoSarlMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NortheastMember" name="NortheastMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TotalReturnBasedOnNetAssetValue" name="TotalReturnBasedOnNetAssetValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TRPAssetsLLCMember" name="TRPAssetsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ScheduleOfEarningsPerShareBasicAndDilutedTable" name="ScheduleOfEarningsPerShareBasicAndDilutedTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IssuanceOfCommonStockNetOfOfferingCosts" name="IssuanceOfCommonStockNetOfOfferingCosts" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AdministrationAgreementMember" name="AdministrationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyFourNotesMember" name="TwentyTwentyFourNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyThreeNotesMember" name="TwentyTwentyThreeNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetPaidInKindInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_OfficeProductsMember" name="OfficeProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentCompanySettlementOfConvertibleNotesPerShare" name="InvestmentCompanySettlementOfConvertibleNotesPerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TotalReturnBasedOnMarketValueWithReinvestmentOfDividends" name="TotalReturnBasedOnMarketValueWithReinvestmentOfDividends" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_IncreaseDecreaseInDistributableEarnings" name="IncreaseDecreaseInDistributableEarnings" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_OriginalIssueDiscountNetOfAccretion" name="OriginalIssueDiscountNetOfAccretion" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_TruckLiteCoLlcMember" name="TruckLiteCoLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesInterestIncome" name="InvestmentsInAndAdvancesToAffiliatesInterestIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_HeritageEnvironmentalServicesIncMember" name="HeritageEnvironmentalServicesIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DebtConversionPrincipalAmount" name="DebtConversionPrincipalAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PingIdentityCorporationMember" name="PingIdentityCorporationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HotelGamingAndLeisureMember" name="HotelGamingAndLeisureMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" name="PercentageOfPreIncentiveFeeNetInvestmentIncomeQuarterlyAfterCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_NetUnrealizedGainsOnInvestments" name="NetUnrealizedGainsOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_EducationMember" name="EducationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfNetProceedsOfSaleOfEquityInterests" name="PercentageOfNetProceedsOfSaleOfEquityInterests" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DividendsTextBlock" name="DividendsTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" name="InvestmentsInAndAdvancesToAffiliatesAtFairValueNetChangeInUnrealizedGainLoss" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_OffsettingAssetsAndLiabilitiesPolicyTextBlock" name="OffsettingAssetsAndLiabilitiesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_OtherMember" name="OtherMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyNineNotesMember" name="TwentyTwentyNineNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapFiveMember" name="InterestRateSwapFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapFourMember" name="InterestRateSwapFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" name="PercentageOfAllPreIncentiveFeeNetInvestmentIncomeAfterCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PassportLabsIncMember" name="PassportLabsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BlackScholesModelMember" name="BlackScholesModelMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapElevenMember" name="InterestRateSwapElevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfInvestmentsAtFairValue" name="PercentageOfInvestmentsAtFairValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" name="PercentageOfManagementFeeInExcessOfAnnualRateOnGrossAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_BaseDividendMember" name="BaseDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CommunicationsMember" name="CommunicationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetwrixCorpMember" name="NetwrixCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolverMember" name="RevolverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" name="InvestmentCompanyNetAssetFromOperationsIncreaseDecrease" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_AmericanAchievementCorpMember" name="AmericanAchievementCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BusinessServicesMember" name="BusinessServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetRealizedGainsLossesOnForeignCurrencyTransactions" name="NetRealizedGainsLossesOnForeignCurrencyTransactions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_InvestmentAdvisoryAgreementMember" name="InvestmentAdvisoryAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentDueDate" name="InvestmentDueDate" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_InvestmentCompanyIssuanceAndRepurchasePerShare" name="InvestmentCompanyIssuanceAndRepurchasePerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DelayedDrawAndRevolverMember" name="DelayedDrawAndRevolverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityAndOtherInvestmentsMember" name="EquityAndOtherInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" name="PercentageOfExcessPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_IncentiveFeesRealizedAndPayableToAdvisor" name="IncentiveFeesRealizedAndPayableToAdvisor" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" name="PercentageOfExcessCatchUpProvisionForPreIncentiveFeeNetInvestmentIncome" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DividendsPolicyTextBlock" name="DividendsPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SignificantAccountingPoliciesLineItems" name="SignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" name="InvestmentsInAndAdvancesToAffiliatesAtFairValueRealizedGainLoss" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" name="PercentageOfPreIncentiveFeeNetInvestmentIncomePayableAfterHurdleRateReachedAndCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" name="RevolvingCreditFacilityMaturityOnJuneTwelveTwoThousandAndTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NondeductibleFederalExciseTaxPercentage" name="NondeductibleFederalExciseTaxPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ControlledAffiliatedInvestmentsMember" name="ControlledAffiliatedInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" name="IncentiveFeesAccruedRelatedToExpenseReversalCapitalGainsFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_BanyanSoftwareHoldingsLlcMember" name="BanyanSoftwareHoldingsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DelayedDrawAndMembershipInterestMember" name="DelayedDrawAndMembershipInterestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherIncomePolicyTextBlock" name="OtherIncomePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" name="FairValueOfSecuritiesAsPercentageOfNetAssetsInPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" name="TwoThousandTwentyFourTwentySixTwentyEightAndTwentyNineNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RapidDataGmbhUnternehmensberatungMember" name="RapidDataGmbhUnternehmensberatungMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfIncentiveFeeRate" name="PercentageOfIncentiveFeeRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" name="ScheduleOfComponentOfCarryingValueOfConvertibleNotesAndInterestRateTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock" name="SummaryOfReconciliationIncreaseInNetAssetsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_KyribaCorpMember" name="KyribaCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetTransfersWithinLevel3" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FullsteamOperationsLlcMember" name="FullsteamOperationsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwaps" name="InterestRateSwaps" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" name="TaxRefundFromOperatingLossCarrybackToPreviousTaxYears" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnFebruary42026Member" name="RevolvingCreditFacilityMaturityOnFebruary42026Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BenNevisMidcoLimitedMember" name="BenNevisMidcoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IbisIntermediateCoMember" name="IbisIntermediateCoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MarketingServicesMember" name="MarketingServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ScheduleOfComponentsOfInterestExpenseTableTextBlock" name="ScheduleOfComponentsOfInterestExpenseTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SwapSettlement" name="SwapSettlement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_OrdinaryIncome" name="OrdinaryIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_CoupaHoldingsLLCMember" name="CoupaHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SkylarkUkDebtcoLimitedMember" name="SkylarkUkDebtcoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyTwoConvertibleNotesMember" name="TwentyTwentyTwoConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PartnershipInterestOwnershipPercentage" name="PartnershipInterestOwnershipPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AdviserMember" name="AdviserMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapTwelveMember" name="InterestRateSwapTwelveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AxonifyIncMember" name="AxonifyIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" name="IndebtednessCouldAdverselyAffectBusinessFinancialConditionsOrResultsOfOperationsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CrewlineBuyerIncMember" name="CrewlineBuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnJanuary312025Member" name="RevolvingCreditFacilityMaturityOnJanuary312025Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_FirstLienDebtInvestmentsMember" name="FirstLienDebtInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" name="SummaryOfSharesNewlyIssuedToShareholdersWhoHaveNotOptedOutOfDividendReinvestmentPlanTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_EquityAndOtherInvestments" name="EquityAndOtherInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_NetExpenseForFederalExciseTax" name="NetExpenseForFederalExciseTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FairValueOfAnEffectiveHedge" name="FairValueOfAnEffectiveHedge" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" name="MinimumPercentageOfVotingSecuritiesInInvestmentPortfolio" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ChemicalsMember" name="ChemicalsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HippoXpaBidcoAbMember" name="HippoXpaBidcoAbMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LaramieEnergyLLCMember" name="LaramieEnergyLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EquityOfferingExpensesPolicyTextBlock" name="EquityOfferingExpensesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SignificantAccountingPoliciesTable" name="SignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" name="IncentiveFeesOnNetCapitalGainsAccruedToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_DividendsPayableDateOfSharesIssuedDayMonthAndYear" name="DividendsPayableDateOfSharesIssuedDayMonthAndYear" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_InvestmentCompanyRepurchaseOfDebtPerShare" name="InvestmentCompanyRepurchaseOfDebtPerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" name="PercentageOfPreIncentiveFeeNetInvestmentIncomeHurdleRateQuarterly" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_CostModelMember" name="CostModelMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WranglerTopcoLlcMember" name="WranglerTopcoLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AsgIiLlcMember" name="AsgIiLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PrimeRevenueIncMember" name="PrimeRevenueIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SupplementalDividendMember" name="SupplementalDividendMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" name="PercentageOfExcessPreIncentiveFeeNetInvestmentIncomeForImmediatePrecedingCalendarQuarter" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DelayedDrawRevolverEquityMember" name="DelayedDrawRevolverEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CurrentMarketPricePerSharePercentage" name="CurrentMarketPricePerSharePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_NetExpenseForFederalExciseTaxAndOtherTaxes" name="NetExpenseForFederalExciseTaxAndOtherTaxes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_UnRealizedInvestmentGainsLossesAbstract" name="UnRealizedInvestmentGainsLossesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapThreeMember" name="InterestRateSwapThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherExpensesNotCurrentlyDeductible" name="OtherExpensesNotCurrentlyDeductible" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_HirevueIncMember" name="HirevueIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyEightNotesMember" name="TwoThousandTwentyEightNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OutsystemsLuxcoMember" name="OutsystemsLuxcoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" name="IncentiveFeesOnNetInvestmentIncomePayableToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_InterestRateSwapThirteenMember" name="InterestRateSwapThirteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BearOpCoLLCMember" name="BearOpCoLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GalileoParentincMember" name="GalileoParentincMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LineOfCreditFacilityExtendedDate" name="LineOfCreditFacilityExtendedDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ArrowbuyerIncMember" name="ArrowbuyerIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" name="ReimbursementOfTransactionRelatedExpensesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock" name="SummaryOfTaxCharacterOfShareholderDistributionsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ManagementFeeWaiverHurdle" name="ManagementFeeWaiverHurdle" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PdiTaHoldingsIncMember" name="PdiTaHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BCTOAcePurchaserIncMember" name="BCTOAcePurchaserIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" name="ValueOfInvestmentDeclinesManagementFeeAndIncentiveFeeWillBePayableToAdviserMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ValuationTechniqueCostOfInvestmentsMember" name="ValuationTechniqueCostOfInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyNineNotesMember" name="TwoThousandTwentyNineNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_HumanResourceSupportServicesMember" name="HumanResourceSupportServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherPayablesToAffiliate" name="OtherPayablesToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_LeantaasHoldingsIncMember" name="LeantaasHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" name="UpfrontPaymentsReceiptsInDerivativeAssetsAndLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_LucidworksIncMember" name="LucidworksIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" name="DeferredTaxLiabilityPertainingToUnrealizedGainsRelatedToInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_IRGSEHoldingCorpMember" name="IRGSEHoldingCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfNonQualifyingAssets" name="PercentageOfNonQualifyingAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TaxReclassificationOfStockholdersEquity" name="TaxReclassificationOfStockholdersEquity" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_HornetsecurityHoldingGmbhMember" name="HornetsecurityHoldingGmbhMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EdgeBidcoBVMember" name="EdgeBidcoBVMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TaxableIncome" name="TaxableIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnApril242029Member" name="RevolvingCreditFacilityMaturityOnApril242029Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NonControlledNonAffiliatedInvestmentsMember" name="NonControlledNonAffiliatedInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapOneMember" name="InterestRateSwapOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolverEquityMember" name="RevolverEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestAndDividendIncomeRecognitionPolicyTextBlock" name="InterestAndDividendIncomeRecognitionPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AccountingStandardsUpdate202206Member" name="AccountingStandardsUpdate202206Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AssetValuationWaterfallMember" name="AssetValuationWaterfallMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" name="IncreaseDecreaseInIncentiveFeesOnNetCapitalGainsAccruedToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_ReliaQuestHoldingsLLCMember" name="ReliaQuestHoldingsLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapTenMember" name="InterestRateSwapTenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsOwnedEstimatedCostBasis" name="InvestmentsOwnedEstimatedCostBasis" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_UndistributedNetInvestmentIncomeTaxBasis" name="UndistributedNetInvestmentIncomeTaxBasis" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_InterestRateSwapSevenMember" name="InterestRateSwapSevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NonControlledAffiliatedInvestmentsMember" name="NonControlledAffiliatedInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" name="MinimumPercentageOfInvestmentCompanyTaxableIncomeDistributeToStockholdersInEachTaxableYearToQualifyAsRIC" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_ArtisanBidcoIncMember" name="ArtisanBidcoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PaidInKindInterestIncome" name="PaidInKindInterestIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_TwoThousandTwentyThreeNotesMember" name="TwoThousandTwentyThreeNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ProceedsFromInvestmentsNet" name="ProceedsFromInvestmentsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_AdditionalAggregatePrincipalAmount" name="AdditionalAggregatePrincipalAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PercentageOfCapitalGainsFromApril12024HurdleRate" name="PercentageOfCapitalGainsFromApril12024HurdleRate" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_LegislationAllowsToIncurAdditionalLeverageMember" name="LegislationAllowsToIncurAdditionalLeverageMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" name="AbilityToEnterIntoTransactionsWithAffiliatesIsRestrictedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RetailAndConsumerProductsMember" name="RetailAndConsumerProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_CordanceOperationsLlcMember" name="CordanceOperationsLlcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncreaseDecreaseInAdditionalPaidInCapital" name="IncreaseDecreaseInAdditionalPaidInCapital" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_RepaymentsOnInvestments" name="RepaymentsOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_ManagementAndIncentiveFeeWaived" name="ManagementAndIncentiveFeeWaived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_ExtraHopNetworksIncMember" name="ExtraHopNetworksIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SlBuyerCorpMember" name="SlBuyerCorpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AdjustmentsAbstract" name="AdjustmentsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" name="BorrowMoneyWhichMagnifiesPotentialForGainOrLossAndIncreasesRiskOfInvestingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentySixNotesMember" name="TwentyTwentySixNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" name="RealizedCapitalGainsAccruedPriorToMarchThirtyFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EstimatedGrossUnrealizedLossOnTaxCostInvestment" name="EstimatedGrossUnrealizedLossOnTaxCostInvestment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" name="FairValueOfSecuritiesAsPercentageOfNetAssetsAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_MarcuraEquitiesLtdMember" name="MarcuraEquitiesLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_GainLossFormAdjustmentOfPaidInKindInterest" name="GainLossFormAdjustmentOfPaidInKindInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" name="CapitalGainsAccrueFollowingMarchThirtyFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DividendsDeclaredFromNetInvestmentIncomePerShare" name="DividendsDeclaredFromNetInvestmentIncomePerShare" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder" name="PercentageOfOrdinaryIncomeQualifiedAsInterestRelatedDividendExemptFromDomesticWithholdingTaxApplicableToForeignShareholder" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_AutomotiveMember" name="AutomotiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditInvestmentsMember" name="StructuredCreditInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapTwoMember" name="InterestRateSwapTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolverAndPartnershipInterestMember" name="RevolverAndPartnershipInterestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InvestmentsAtFairValueTextBlock" name="InvestmentsAtFairValueTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" name="SummaryOfGeographicCompositionOfInvestmentsAtFairValueTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_EstimatedGrossUnrealizedGainsOnTaxCostInvestment" name="EstimatedGrossUnrealizedGainsOnTaxCostInvestment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisAssetNetAmortizationOfDiscountOnSecurities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_ManufacturingMember" name="ManufacturingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" name="PercentageOfManagementFeeInExcessOfQuarterRateOnGrossAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_UndistributedNetRealizedGainsTaxBasis" name="UndistributedNetRealizedGainsTaxBasis" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_IncentiveFeesOnNetCapitalGains" name="IncentiveFeesOnNetCapitalGains" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_DelayedDrawRevolverPreferredEquityMember" name="DelayedDrawRevolverPreferredEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EDBParentLLCMember" name="EDBParentLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_ApteanIncMember" name="ApteanIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RevolvingCreditFacilityMaturityOnApril232027Member" name="RevolvingCreditFacilityMaturityOnApril232027Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_BlueSnapIncMember" name="BlueSnapIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" name="PercentageOfMinimumQualifyingAssetsToPurchaseNonQualifyingAssets" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_RisksAssociatedWithChangesInInterestRatesMember" name="RisksAssociatedWithChangesInInterestRatesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" name="TwoThousandTwentyFourTwentySixAndTwentyEightNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" name="TwoThousandTwentyThreeAndTwentyFourAndTwentySixNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" name="PercentageOfAllRemainingPreIncentiveFeeNetInvestmentIncomeQuarterly" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DelayedDrawMember" name="DelayedDrawMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InternetServicesMember" name="InternetServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_WestMember" name="WestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentySixNotesMember" name="TwoThousandTwentySixNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetExpense" name="NetExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" name="ProceedsFromSettlementsOfInterestRateSwapsExcludingUpfrontFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_BabylonFincoLimitedMember" name="BabylonFincoLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapNineMember" name="InterestRateSwapNineMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_StructuredCreditInvestments" name="StructuredCreditInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_PurchaseCommitmentToFundInvestment" name="PurchaseCommitmentToFundInvestment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_IncreaseDecreaseInManagementFeesPayableToAffiliate" name="IncreaseDecreaseInManagementFeesPayableToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_InsuranceMember" name="InsuranceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PurchasesAndOriginationsOfInvestmentsNet" name="PurchasesAndOriginationsOfInvestmentsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_ElysianFincoLtdMember" name="ElysianFincoLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DividendsDeclaredDuringThePeriod" name="DividendsDeclaredDuringThePeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_InvestmentsInAndAdvancesToAffiliatesOtherIncome" name="InvestmentsInAndAdvancesToAffiliatesOtherIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" name="AbilityToRaiseAdditionalCapitalDueToRegulationGovernanceOnBdcMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AlphaMidcoIncMember" name="AlphaMidcoIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" name="PaymentsForSettlementsOfInterestRateSwapsExcludingUpfrontFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_TaxCostOfInvestments" name="TaxCostOfInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_UnrealizedGainsLossesOnIncomeTaxProvision" name="UnrealizedGainsLossesOnIncomeTaxProvision" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" name="PercentageOfPreIncentiveFeeNetInvestmentIncomeAnnualizedAfterCatchUpAchieved" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DerivativeNotionalAmountHeldDuringPeriod" name="DerivativeNotionalAmountHeldDuringPeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_TotalReturnBasedOnMarketValue" name="TotalReturnBasedOnMarketValue" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="tslx_EMSLinqIncMember" name="EMSLinqIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" name="NetChangeInUnrealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" name="ScheduleOfCommitmentsToFundInvestmentsInCurrentPortfolioCompaniesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_LongTermCapitalGains" name="LongTermCapitalGains" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_InvestmentsFairValueDisclosureNet" name="InvestmentsFairValueDisclosureNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" name="PercentageOfPreIncentiveFeeNetInvestmentIncomePayableQuarterly" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_DelayedDrawEquityMember" name="DelayedDrawEquityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncentiveFeesOnNetInvestmentIncome" name="IncentiveFeesOnNetInvestmentIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_TangoManagementConsultingLLCMember" name="TangoManagementConsultingLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_EmploymentHeroHoldingsPtyLtdMember" name="EmploymentHeroHoldingsPtyLtdMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_UnrealizedLossOnInvestments" name="UnrealizedLossOnInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_InterestRateSwapEightMember" name="InterestRateSwapEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" name="RealizedCapitalGainsAccruedBeginningAprilFirstTwoThousandFourteenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" name="IncreaseDecreaseInIncentiveFeesOnNetInvestmentIncomePayableToAffiliate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_PerShareMarketValueAtEndPeriod" name="PerShareMarketValueAtEndPeriod" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" name="Debtinstrumentdescriptionoflondoninterbankofferedrateliborvariableratebasis" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_Project44IncMember" name="Project44IncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_LeverageWaiverMember" name="LeverageWaiverMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AzuriteIntermediateHoldingsIncMember" name="AzuriteIntermediateHoldingsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwentyTwentyEightNotesMember" name="TwentyTwentyEightNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_OtherTemporaryDifferences" name="OtherTemporaryDifferences" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_BayshoreIntermediate2LPMember" name="BayshoreIntermediate2LPMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_IncreaseDecreaseInInterestReceivablePaidInKind" name="IncreaseDecreaseInInterestReceivablePaidInKind" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_LineOfCreditFacilityStatedMaturityDate" name="LineOfCreditFacilityStatedMaturityDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_MezzanineDebtInvestmentsMember" name="MezzanineDebtInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_TwoThousandTwentyFourNotesMember" name="TwoThousandTwentyFourNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AgreementTerminationPeriodWithoutPenalty" name="AgreementTerminationPeriodWithoutPenalty" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_TransportationMember" name="TransportationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock" name="SummaryOfIndustryCompositionOfInvestmentsAtFairValueTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="tslx_InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" name="InvestmentOwedOnPrincipalAmountOutstandingAndAccruedInterest" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="tslx_NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" name="NetRealizedGainsLossesOnInvestmentsAndForeignCurrencyTranslation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="tslx_AlaskaBidcoOyMember" name="AlaskaBidcoOyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_InterestRateSwapSixMember" name="InterestRateSwapSixMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_SecondLienDebtInvestmentsMember" name="SecondLienDebtInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_DiscoParentIncMember" name="DiscoParentIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="tslx_AssetCoveragePercentage" name="AssetCoveragePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
</xsd:schema>
