The title compound, C9H9N3O2S, is a monoclinic (C2/c) polymorph of the previously reported triclinic structure [Kang (2013 ▶). Acta Cryst. E69, o1327]. The mol-ecule is almost planar with an r.m.s. deviation of 0.069 Å from the mean plane of all non-H atoms. The benzoyl and terminal thio-urea fragments adopt a transoid conformation with respect to the central carbonyl O atom. Two intra-molecular N-H⋯O hydrogen bonds are present. In the crystal, N-H⋯O and N-H⋯S inter-actions link the mol-ecules into zigzag chains extending along the c-axis direction.