Filed pursuant to Rule 497(a)

Registration No. 333-263258

Rule 482ad

[TEXT OF COMMUNICATION SENT VIA BLOOMBERG]

GUIDANCE: Main Street $300m 5Y +310a (+/-5)

By Brian Smith and Bloomberg Automation

(Bloomberg) -- Expected to price today.

•$300m 5Y Fixed (March 1, 2029) +310a (+/-5) IPT +335 area

•Issuer: Main Street Capital Corp (MAIN) Exp. Ratings: BBB-/BBB- (S&P/Fitch) Format: SEC registered, senior unsecured CoC 100, 1-month par call, MWC

•UOP: Repay outstanding indebtedness, including amounts outstanding under its Credit Facilities or its May 2024 Notes

•Settlement: Jan. 12, 2024 (T+2) Denoms: 2k x 1k

•Bookrunners: JPM, RBC, SMBC, TSI See security information: 5Y Fixed

•Information from person familiar with the matter, who asked not to be identified because they're not authorized to speak about it

See all preliminary issues: PREL <GO>

Related ticker:

MAIN US (Main Street Capital Corp)

To contact the reporter on this story:

Brian Smith in New York at bsmith373@bloomberg.net

This story was produced with the assistance of Bloomberg Automation.