In the title compound, C(15)H(13)N(3)O(3)S, the C-S-N(H)-N linkage is non-planar, the torsion angle being -65.12 (13)° and the S atom showing a tetra-hedral environment. The compound has two almost planar fragments linked to the S atom: the isatin-derivative fragment [(C(8)H(5)NO)N-N(H)-] and the tolyl fragment [C(7)H(7)-] have maximum deviations from the mean plane through the non-H atoms of 0.0813 (13) and 0.0094 (16) Å, respectively, and make an inter-planar angle of 80.48 (3)°. In the crystal, mol-ecules are connected into inversion dimers via pairs of N-H⋯O hydrogen bonds. Additionally, the mol-ecular structure is stabilized by an intra-molecular N-H⋯O hydrogen bond.