Main Street Capital Investor Presentation Deck

MAIN maintains a conservative capital structure, with limited overall leverage and an intentional mix of secured, floating rate revolving debt and unsecured, fixed rate long-term debt E Stable, Long-Term Leverage - Significant Unused Capacity Facility $980.0 million Corporate Facility $255.0 million SPV Facility(2)(3) Notes Payable Capital structure is designed to correlate to and complement the expected duration and fixed/floating rate Notes Payable nature of investment portfolio assets Notes Payable SBIC Debentures Interest Rate SOFR+1.875% floating (6.6% (4)) SOFR+2.50% floating (7.3% (4)) 3.00% fixed 5.20% fixed 7.74% (5) fixed (weighted average) 2.87% fixed (weighted average) Maturity August 2027(1) MAIN ST November 2027(²) CAPITAL CORPORATION Redeemable at MAIN's option at any time, subject to certain make whole provisions; Matures July 14, 2026 Redeemable at MAIN's option at any time, subject to certain make whole provisions; Matures May 1, 2024 Redeemable at MAIN's option at any time, subject to certain make whole provisions; Matures December 23, 2025 Various dates between 2023 - 2031 (weighted average duration = 5.1 years) Principal Drawn $394.0 million $170.0 million $500.0 million $450.0 million $150.0 million $334.0 million (1) As of March 31, 2023, MAIN maintained a corporate revolving line of credit (the Corporate Facility), which had $980.0 million in total commitments with an accordion feature with the right to request an increase up to $1.4 billion; MAIN's Corporate Facility is fully revolving until August 2026, with a maturity date in August 2027 (2) As of March 31, 2023, MAIN tained a secured special purpose veh financing facility (the SPV Facility), which had $255.0 million in total co tments with an accordion feature with the right to request an increase up to $450.0 million; MAIN's SPV Facility is fully revolving until November 2025, with a maturity date in November 2027 (3) Borrowings under the Corporate Facility and the SPV Facility (together, the Credit Facilities) are available to provide additional liquidity for investment and operational activities (4) Credit Facilities' rates reflect the rate based on SOFR as of March 31, 2023 and effective as of the contractual reset date as of April 1, 2023 (5) Based upon $100.0 million and $50.0 million in aggregate principal amount bearing interest at 7.84% and 7.53%, respectively Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 42

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