Exhibit 99.1 K FIRST QUARTER 2024 EARNINGS RESULTS Sixth Street Specialty Lending, Inc. Reports First Quarter Results; Declares a Second Quarter Base Dividend Per Share of $0.46, and a First Quarter Supplemental Dividend Per Share of $0.06. NEW YORK — May 1, 2024 — Sixth Street Specialty Lending, Inc. (NYSE: TSLX, or the "Company") today reported net investment income of $0.59 per share and net income of $0.53 per share for the first quarter ended March 31, 2024. These results correspond to an annualized re ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2024 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 001-36364 Sixth Street Specialty Lending, Inc. (Exact name of registrant as specified in its charter) Delaware 27-3380000 (State or ot ...

Sixth Street Specialty Lending, Inc. (NYSE:TSLX) Q4 2023 Earnings Conference Call February 16, 2024 8:30 AM ET Company Participants Cami VanHorn - Head of Investor Relations Joshua Easterly - Chief Executive Officer Bo Stanley - President Ian Simmonds - Chief Financial Officer Conference Call Participants Mickey Schleien - Ladenburg Thalmann Brian McKenna - Citizens JMP Finian O'Shea - Wells Fargo Kenneth Lee - RBC Capital Markets Melissa Wedel - JPMorgan Erik Zwick - Hovde Group Robert Dodd - Raymond James ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K ☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 Commission file number 001-36364 Sixth Street Specialty Lending, Inc. (Exact Name of Registrant as Specified in Its Charter) | Delaware | | --- | (State or other jurisdiction of incorporation or organizati ...

Financial Data and Key Metrics Changes - For Q3 2023, the adjusted net investment income per share was $0.60, corresponding to an annualized return on equity of 14.4%, while the adjusted net income per share was $0.77, corresponding to an annualized return on equity of 18.5% [48][69] - The net asset value per share increased to $16.97, up $0.23 or 1.4% from the previous quarter [10][63] - Total investments reached $3.1 billion, with total principal debt outstanding at $1.7 billion and net assets at $1.5 billion [63] Business Line Data and Key Metrics Changes - The portfolio's weighted average yield on debt income-producing securities increased from 14.1% to 14.3% due to higher interest rates [61] - New investment opportunities represented 97% of total fundings for the quarter, with only 3% supporting upsizes to existing portfolio companies [58] - The company had $206 million of commitments and $152 million of fundings across eight new and two upsizes to existing portfolio companies [26] Market Data and Key Metrics Changes - The total amount of outstanding in the leveraged loan index declined by $23 billion or 1.6% over the last 12 months, marking the first year of year-over-year decline since the global financial crisis [23] - Approximately one-third of CLOs are now out of their investment period, expected to increase to about 40% by year-end [12] Company Strategy and Development Direction - The company is focused on capital deployment in a higher-for-longer interest rate environment, emphasizing disciplined capital allocation and asset selection [20][21] - There is an expectation of a structural shift towards direct lending, with opportunities arising from the $130 billion of leverage loans maturing by the end of 2025 [24] - The company aims to differentiate returns for shareholders through strong asset selection and portfolio management capabilities [21] Management's Comments on Operating Environment and Future Outlook - Management noted that while there are signs of consumer weakening, the portfolio remains insulated from consumer discretionary trends due to its B2B focus [29] - The company anticipates that the lagged impact of higher rates may lead to increased defaults and losses in the next 12 to 15 months [52][105] - Management expressed confidence in the ability to navigate the current economic challenges and maintain strong performance [72] Other Important Information - The company declared a base quarterly dividend of $0.46 per share and a supplemental dividend of $0.07 per share related to Q3 earnings [53] - Non-accruals were minimal at 0.7% of the portfolio at fair value, with no new portfolio companies added to non-accrual status from the prior quarter [31] Q&A Session Summary Question: State of the Union on Sponsor Side - Management indicated that sponsors continue to support their businesses despite some signs of weakening in consumer demand [44][75] Question: Impact of Higher Rates on Credit Differentiation - Management expects differentiation in shareholder experience based on credit losses to manifest in the next 12 to 15 months, with private credit likely outperforming broadly syndicated credit [105][106] Question: Interest Coverage and Portfolio Upsizing - Interest coverage across the portfolio is about two times, with a slight decline noted [98] - The low upsizing activity was attributed to an anemic M&A market rather than pressure on companies [100] Question: Quality of Deals Refinanced from Broadly Syndicated Loan Market - Management clarified that not all deals moving to private credit are adverse selections, as different sponsors have varying needs for capital [129] Question: Recovery of Spread Tightening - Management estimated that the portfolio is about two-thirds of the way through recovering from spread widening experienced in 2022 [117]

References in this presentation ("Presentation") to "TSLX," "we," "us," "our" and "the Company" refer to Sixth Street Specialty Lending, Inc. The following slides contain summaries of certain financial and statistical information about TSLX. The information contained in this Presentation is summary information that is intended to be considered in the context of our Securities and Exchange Commission filings and other public announcements that we may make, by press release or otherwise, from time to time. We ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934. For the quarterly period ended September 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934. For the transition period from to Commission File Number 001-36364 Sixth Street Specialty Lending, Inc. (Exact name of registrant as specified in its charter) Delaware 27-3380000 (State ...

Sixth Street Specialty Lending, Inc. (NYSE:TSLX) Q2 2023 Earnings Conference Call August 4, 2023 8:30 AM ET Company Participants Cami VanHorn – Head-Investor Relations Joshua Easterly – Chief Executive Officer Bo Stanley – President Ian Simmonds – Chief Financial Officer Michael Fishman – Vice President Conference Call Participants Finian O’Shea – WFS Robert Dodd – Raymond James Ken Lee – RBC Capital Markets Melissa Wedel – JPMorgan Mark Hughes – Truist Ryan Lynch – KBW Operator Good morning, and welcome to ...

S I X T H S T R E E T S P E C I A L T Y L E N D I N G Quarter Ended June 30, 2023 EARNINGS PRESENTATION DISCLAIMER AND FORWARD-LOOKING STATEMENT References in this presentation ("Presentation") to "TSLX," "we," "us," "our" and "the Company" refer to Sixth Street Specialty Lending, Inc. This Presentation includes forward-looking statements about TSLX that involve substantial risks and uncertainties. These forward-looking statements are not historical facts, but rather are based on current expectations, estim ...

UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, DC 20549 FORM 10-Q (Mark One) ☒ QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934. For the quarterly period ended June 30, 2023 OR ☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934. For the transition period from to Commission File Number 001-36364 Sixth Street Specialty Lending, Inc. (Exact name of registrant as specified in its charter) Delaware 27-3380000 (State or o ...