Main Street Investor Presentation

MAIN Financial Performance Total Investment Income ($ in millions) Year over Year Growth MAINST CAPITAL CORPORATION Distributable Net Investment Income(3) ($ in millions) Year over Year Growth 8% 15% 13% 4% (12)%(1) 10% 17% 14% 1% (12)%(1) $260.0 $180.0 $240.0 $220.0 $243.4 $233.4 $160.0 $165.8 $167.4 $140.0 $200.0 $145.4 $205.7 $180.0 $120.0 $124.11 $178.3 $160.0 $164.6 $113.3 $100.0 $140.0 $120.0 $80.0 $100.0 $108.2 $73.5 $60.0 $80.0 $60.0 $40.0 $40.0 $20.0 $20.0 50.0 $0.0 2015 2016 2017 2018 2019 YTD (2) 2020 2015 2016 2017 2018 2019 YTD (2) 2020 (1) Reflects year-to-date June 30, 2020 performance compared with year-to-date June 30, 2019 performance (2) Through June 30, 2020 (3) See Non-GAAP Information included on page 47 of this presentation. Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 33

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