In the title compound, C(12)H(9)NO(3)S, the isoindoline-1,3-dione group is almost planar, with an r.m.s. deviation of 0.020 Å, whereas the heterocyclic ring approximates to an envelope with the methyl-ene group not adjacent to the S atom in the flap position. A short intra-molecular C-H⋯O contact generates an S(6) ring motif. In the crystal structure, weak aromatic π-π stacking inter-actions occur between the centroids of the benzene rings at a distance of 3.558 (2) Å.