X0609 4 2026-07-30 0001624322 Business First Bancshares, Inc. BFST 0001734773 MANSFIELD KEITH false 500 LAUREL STREET, SUITE 101 BATON ROUGE LA 70801 1 EVP&COO of b1Bank 0 COMMON STOCK 2026-07-30 4 S 0 4200 32.08 D 77139 D Restricted Stock Units 0.0000 Common Stock 13374 13374 D This transaction was executed in multiple trades at prices ranging from $31.98 to $32.14. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide upon request to the SEC staff, the issuer or a securityholder of the issuer full information regarding the number of shares and prices at which the transaction was effected. Includes 27,000 shares held by the reporting person's investment retirement account. Includes: (a) 3,722 time-based restricted stock units granted to the reporting person on December 12, 2024, which will vest in two substantially equal installments on the second and third anniversary of the issuance date; (b) 3,912 time-based restricted stock units granted to the reporting person on March 1, 2025, which will vest in two substantially equal installments on the second and third anniversary of the issuance date; and (c) 5,740 time-based restricted stock units granted to the reporting person on March 2, 2026, which will vest in three substantially equal installments on the first, second, and third anniversary of the issuance date. /s/ Heather Roemer, as attorney-in-fact for Keith Mansfield 2026-07-31