In the title compound, C11H15N3O2S, the dihedral angle between the mean planes of the benzene ring and hydrazinecarbo-thio-amide group is 9.2 (1)°. An intra-molecular O-H⋯N hydrogen bond is observed, serving to maintain an approximately planar conformation for the molecule. In the crystal, inversion dimers linked by C-H⋯O inter-actions occur. Further C-H⋯O contacts link dimers into (010) chains.