In the title compound, C(17)H(16)ClN(3)O(2)S, the dihedral angle between the benzene rings is 7.75 (13)°. The thia-zine ring adopts an envelope conformation with the S atom as the flap at a distance of 0.813 (2) Å from the plane through the other five atoms. In the crystal, C-H⋯O hydrogen bonds link the mol-ecules into chains propagating in [100].