Exhibit 99.1

| NEWS RELEASE
| Contacts: Main Street Capital Corporation Dwayne L. Hyzak, CEO, dhyzak@mainstcapital.com Ryan R Nelson, CFO, rnelson@mainstcapital.com 713-350-6000 Dennard Lascar Investor Relations Ken Dennard / ken@dennardlascar.com Zach Vaughan / zvaughan@dennardlascar.com 713-529-6600

Main Street Announces Amendment of its Corporate Credit Facility
Total Commitments Increased to $1.240 Billion
Final Maturity Date Extended to June 2031
HOUSTON – June 30, 2026 – Main Street Capital Corporation (NYSE: MAIN) (“Main Street”) is
pleased to announce the amendment of its revolving credit facility (the “Corporate Facility”). The
recently closed amendment provides an increase in total commitments from $1.175 billion to $1.240
billion, while maintaining an expanded accordion feature that allows for an increase up to $1.860
billion of total commitments from new and existing lenders on the same terms and conditions as the
existing commitments and maintaining the benefits of a diversified group of 18 lenders. The
amendment also extends both the revolving period, or reinvestment period, and the final maturity date
through June 2030 and to June 2031, respectively. In addition, Main Street continues to maintain
options under the amended Corporate Facility which could extend each of the revolving period and the
final maturity of the Corporate Facility for up to two additional years, subject to certain conditions,
including lender approval.
ABOUT MAIN STREET CAPITAL CORPORATION
Main Street (www.mainstcapital.com) is a principal investment firm that primarily provides
customized long-term debt and equity capital solutions to lower middle market companies and debt
capital to private companies owned by or in the process of being acquired by a private equity fund.
Main Street’s portfolio investments are typically made to support management buyouts,
recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse
industry sectors. Main Street seeks to partner with entrepreneurs, business owners and management
teams and generally provides customized “one-stop” debt and equity financing solutions within its
lower middle market investment strategy. Main Street seeks to partner with private equity fund
sponsors and primarily invests in secured debt investments in its private loan investment strategy.
Main Street’s lower middle market portfolio companies generally have annual revenues between $10
million and $150 million. Main Street’s private loan portfolio companies generally have annual
revenues between $25 million and $500 million.
Main Street, through its wholly-owned portfolio company MSC Adviser I, LLC (“MSC Adviser”),
also maintains an asset management business through which it manages investments for external
parties. MSC Adviser is registered as an investment adviser under the Investment Advisers Act of
1940, as amended.
FORWARD-LOOKING STATEMENTS
This press release contains certain forward-looking statements, including but not limited to the
availability of future financing capacity under the Corporate Facility, which are based upon Main
Street management’s current expectations and are inherently uncertain. Any such statements other than
statements of historical fact are likely to be affected by other unknowable future events and conditions,
including elements of the future that are or are not under Main Street’s control, and that Main Street
may or may not have considered; accordingly, such statements cannot be guarantees or assurances of
any aspect of future performance. Actual performance, events and results could vary materially from
these estimates and projections of the future as a result of a number of factors, including those
described from time to time in Main Street’s filings with the Securities and Exchange Commission.
Such statements speak only as of the time when made and are based on information available to Main
Street as of the date hereof and are qualified in their entirety by this cautionary statement. Main Street
assumes no obligation to revise or update any such statement now or in the future.
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