X0508 4 2026-03-01 0001624322 Business First Bancshares, Inc. BFST 0001734773 MANSFIELD KEITH 500 LAUREL STREET, SUITE 101 BATON ROUGE LA 70801 1 EVP&COO of b1Bank 0 COMMON STOCK 2026-03-01 4 M 0 1926 A 83339 D COMMON STOCK 2026-03-01 4 F 0 676 27.30 D 82663 D Restricted Stock Units 2026-03-01 4 M 0 1926 D Common Stock 1926 7634 D Restricted Stock Units 0 2026-03-02 4 A 0 5740 A Common Stock 5740 13374 D Includes 3,776 shares of unvested restricted stock granted on February 1, 2024, which will vest on March 31, 2026. Under the terms of the relevant restricted stock grants, the reported shares of unvested restricted stock are subject to forfeiture upon the occurrence of certain events. Includes 27,000 shares held by the reporting person's investment retirement account. The reporting person received an award of 5,838 time-based restricted stock units on March 1, 2025, vesting in three substantially equal installments on the first, second, and third anniversary of the issuance date. Reflects the grant of 5,740 time-based restricted stock units granted to the reporting person on March 2, 2026, of which 1,913 shares will vest on March 2, 2027, 1,913 shares will vest on March 2, 2028, and the remaining 1,914 shares will vest on March 2, 2029. Each time-based restricted stock unit is economically equivalent to one share of common stock of the issuer. 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 2026-03-03