Material Agreement (Form 8-K)

On September 19, 2025, Golub Capital BDC, Inc. (the "Company") entered into an underwriting agreement (the "Underwriting Agreement") by and among the Company, GC Advisors LLC (the "Adviser"), Golub Capital LLC (the "Administrator"), and RBC Capital Markets, LLC, as the underwriter set forth therein, in connection with the issuance and sale of an additional $250.0 million aggregate principal amount of the Company's 7.050% Notes due 2028 (the "New Notes" and the issuance and sale of the New Notes, the "Offering"). The closing of the Offering is expected to occur on September 26, 2025, subject to customary closing conditions.

The Underwriting Agreement includes customary representations, warranties, and covenants by the Company, the Adviser, and the Administrator. It also provides for customary indemnification by each of the Company, the Adviser, the Administrator, and the underwriter against certain liabilities and customary contribution provisions in respect of those liabilities.

The Offering was made pursuant to the Company's effective shelf registration statement on Form N-2 (File No. 333-286240) previously filed with the Securities and Exchange Commission (the "SEC"), as supplemented by a preliminary prospectus supplement dated September 19, 2025, a final prospectus supplement dated September 19, 2025, and the pricing term sheet filed with the SEC on September 19, 2025. This Current Report on Form 8-K shall not constitute an offer to sell or a solicitation of an offer to buy any securities, nor shall there be any sale of these securities in any state or jurisdiction in which such an offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or other jurisdiction.

The foregoing description of the Underwriting Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of the Underwriting Agreement filed as an exhibit hereto and incorporated by reference herein.