In the mol-ecule of the title compound, C(18)H(13)Cl(2)N(3)O(2)S(2), the thia-zolidinone ring has an envelope conformation with the S atom displaced by 0.394 (3) Å from the plane of the other ring atoms. The thia-diazole ring is oriented at a dihedral angle of 7.40 (4)° with respect to the 4-methoxy-phenyl ring. Intra-molecular C-H⋯S, C-H⋯N and C-H⋯Cl hydrogen bonds result in the formation of two planar and two non-planar five-membered rings. The planar five-membered rings are oriented at a dihedral angle of 6.23 (3)°. The 2,4-dichloro-phenyl ring is oriented at dihedral angles of 84.21 (4) and 83.55 (3)° with respect to the thia-diazole and 4-methoxy-phenyl rings, respectively. In the crystal structure, inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into centrosymmetric dimers.