In the title compound, C16H12ClNOS, the seven-membered thiazepine ring adopts a distorted twisted boat conformation. The dihedral angle between the least-squares planes of the 1,5-benzothiazepine ring system and the benzene ring is 50.2 (1)°. In the crystal, pairs of N—H⋯O hydrogen bonds link centrosymmetrically related molecules into dimers, generating R
2
2(8) ring motifs. The crystal packing is further stabilized by π–π interactions [centroid–centroid distance = 3.763 (2) Å].