In the title compound, C21H13Cl2NO2S, the benzo-thia-zole ring makes dihedral angles of 0.94 (1) and 70.65 (5)° with the 4-chloro-phenyl-methanone unit and the 5-chloro-phenyl ring, respectively. The dihedral angle between the 4-chloro-phenyl-methanone unit and the 5-chloro-phenyl ring is 66.20 (5)°. The crystal structure consists of dimeric units generated by C-H⋯N hydrogen bonds, further linked by C-H⋯O and C-H⋯π inter-actions, leading to a three-dimensional network.