The title compound, C(9)H(9)N(3)S, was synthesized by the reaction of 4-methyl-benzoic acid and thio-semicarbazide. The thia-diazol ring adopts a planar conformation and makes a dihedral angle of 31.19 (18)° with the phenyl ring. In the crystal, mol-ecules are linked by N-H⋯N hydrogen bonds.