Exhibit 99.1 Gladstone Capital Corporation Reports Financial Results for its Second Quarter Ended March 31, 2024 McLean, VA, May 1, 2024: Gladstone Capital Corporation (Nasdaq: GLAD) (the “Company”) today announced earnings for its second fiscal quarter ended March 31, 2024. Please read the Company’s Quarterly Report on Form 10-Q filed today with the U.S. Securities and Exchange Commission (the “SEC”), which is available on the SEC’s website at www.sec.gov and the investors section of the Company’s website ...