☒QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIESEXCHANGE ACT OF 1934 For the quarterly period endedMarch 31,2025OR Sixth Street Specialty Lending, Inc.(Exact name of registrant as specified in its charter) Securities registered pursuant to Section 12(b) of the Act: Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during thepreceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past90 days.Yes☒No☐ Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of RegulationS-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files).Yes☒No☐ Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerginggrowth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2of the Exchange Act. If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revisedfinancial accounting standards provided pursuant to Section 13(a) of the Exchange Act.☐ Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).Yes☐No☒The number of shares of the registrant’s common stock, $.01 par value per share, outstanding at April 30, 2025 was93,964,358. INDEXNO.PART I.FINANCIAL INFORMATION4Item 1.Financial Statements4Consolidated Balance Sheets as of March 31, 2025 (Unaudited) and December 31, 20244Consolidated Statements of Operations for the three months ended March 31, 2025 and 2024 (Unaudited)5Consolidated Schedules of Investments as of March 31, 2025 (Unaudited) and December 31, 20246Consolidated Statements of Changes in Net Assets for the three months ended March 31, 2025 and 2024(Unaudited)24Consolidated Statements of Cash Flows for the three months ended March 31, 2025 and 2024 (Unaudited)25Notes to Consolidated Financial Statements (Unaudited)26Item 2.Management’s Discussion and Analysis of Financial Condition and Results of Operations50Item 3.Quantitative and Qualitative Disclosures About Market Risk70Item 4.Controls and Procedures71PART II.OTHER INFORMATION72Item 1.Legal Proceedings72Item 1A.Risk Factors72Item 2.Unregistered Sales of Equity Securities and Use of Proceeds72Item 3.Defaults Upon Senior Securities72Item 4.Mine Safety Disclosures72Item 5.Other Information72Item 6.Exhibits73SIGNATURES74 CAUTIONARY STATEMENT REGARDING FORWARD-LOOKING STATEMENTS This report contains forward-looking statements that involve substantial risks and uncertainties. These forward-lookingstatements are not historical facts, but rather are based on current expectations, estimates and projections about us, our current andprospective portfolio investments, our industry, our beliefs, and our assumptions. Words such as “anticipates,” “expects,”“intends,” “plans,” “believes,” “seeks,” “estimates,” “would,” “should,” “targets,” “projects,” and variations of these words andsimilar expressions are intended to identify forward-looking statements. These statements are not guarantees of future performanceand are subject to risks, uncertainties, and other factors, some of which are beyond our control and difficult to predict, that couldcause actual results to differ materially from those expressed or forecasted in the forward-looking statements. In addition to factors previously identified elsewhere in the reports and other documents Sixth Street Specialty Lending, Inc. (the"Company", "we", "us", or "our") has filed with the Securities and Exchange Commission, or SEC, the following factors, amongothers, could cause actual results to differ materially from forward-looking statements or historical performance: •an economic downturn, which could impair our portfolio companies’ abilities to continue to operate, and could lead to theloss of some or all of our investments in those portfolio companies;•such an economic downturn could disproportionately impact the companies in which we have invested and others that weintend to target for investment, potentially causing us to experience a decrease in investment opportunities and diminisheddemand for capital from these companies;•such an economic downturn could also impact availability and pricing of our financing;•an inability to access the capital markets could impair our ability to raise capital and our investment activities;•inflation could negatively impact our business, including our ability to access the debt markets on favorable terms, or couldnegatively im