A novel Ag/BiOBr/CeO2 composite was successfully prepared for the first time, which had excellent performance in degrading sulfisoxazole (SSX) under visible light irradiation. The as-prepared samples were characterized by SEM, XRD, UV–vis DRS and BET et al. The composite of 10% Ag/BiOBr/CeO2 showed the best photocatalytic activity and more than 99.5% SSX can be removed within 20 min. It exhibited the highest k value of 0.2428 min−1, which was about 39.7 times higher than pure BiOBr (6.11 × 10−3 min−1) and 22.1 times higher than BiOBr/CeO2 (1.09 × 10−2 min−1), respectively. The addition of Ag significantly improved the absorption rate of visible light and the separation rate of photogenerated electron–hole pairs. The initial pH and dosage of samples could have an influence on the photocatalytic activity. The radical trapping experiments proved that ·O2− and h+ were the main active species involved in photocatalytic degradation. Finally, the synthesized catalyst maintained excellent photocatalytic activity after 5 repeated cycles, which indicated the extraordinary stability and recyclability of Ag/BiOBr/CeO2.Graphical abstract: