QuickLinks -- Click here to rapidly navigate through this document

Exhibit 21.1

LIST OF SUBSIDIARIES

       Main Street Capital Partners, LLC, a Delaware limited liability company

       Main Street Mezzanine Management, LLC, a Delaware limited liability company

       Main Street Equity Interests, Inc., a Delaware corporation

       Main Street Mezzanine Fund, LP, a Delaware limited partnership

       Main Street Capital II GP, LLC, a Delaware limited liability company

       Main Street Capital II, LP, a Delaware limited partnership

       MSCII Equity Interests, LLC, a Delaware limited liability company

QuickLinks

Exhibit 21.1

LIST OF SUBSIDIARIES