Benzoylquinazolinone derivatives 3a–n were synthesized via a simple one‐step reaction, and evaluated for in vitro α‐glucosidase inhibitory activity. Compounds 3d, 3f–g, 3i, and 3m–n showed more inhibitory activity than standard drug acarbose (IC₅₀ = 750.0 ± 1.5 μM), and among them, compound 3d displayed the highest α‐glucosidase inhibitory activity (IC₅₀ = 261.6 ± 0.1 μM). The kinetic analysis of the compound 3d revealed that this compound inhibited α‐glucosidase in a competitive manner (K_i = 255 μM). The docking studies were applied to predict binding modes of the synthesized compounds in active site of α‐glucosidase.