In the title compound, C(16)H(14)N(4)OS, the dihedral angle between the nine-membered 5-methyl-indolin-2-one ring system and the benzene ring is 10.21 (7)°. Intra-molecular cyclic N-H⋯O and C-H⋯S hydrogen-bonding inter-actions [graph set S(6)] are present within the N-N-C-N chain between the ring systems. In the crystal, mol-ecules form centrosymmetric cyclic dimers through pairs of N-H⋯O hydrogen bonds [graph set R(2) (2)(8)].