In the title compound, C(17)H(13)ClN(4)OS, the 1,3,4-thia-diazole ring makes dihedral angles of 9.70 (15) and 7.22 (10)° with the benzene and phenyl rings, respectively; the dihedral angle between these two rings is 6.37 (19)°. In the crystal, pairs of N-H⋯N and C-H⋯O hydrogen bonds between inversion-related mol-ecules result in supra-molecular ribbons displaying alternate R(2) (2)(8) and R(2) (2)(14) graph-set ring motifs.