In the title compound, C12H9ClN4OS, the carbonyl group is at a cis position with respect to the thio-urea unit. The dihedral angle between the phenyl and pyrimidine ring is 16.49 (6)°. An intra-molecular N-H⋯N hydrogen bond stabilizes the mol-ec-ular conformation. In the crystal, N-H⋯N, C-H⋯O and C-H⋯S hydrogen bonds generate chains along the bc axis.