In the title compound, C16H13NO3S, the plane of the naphthalene ring system forms a dihedral angle of 64.66 (10)° with the benzene ring. The molecular structure is stabilized by weak intramolecular C—H⋯O interactions and the crystal packing is stabilized by weak intermolecular N—H⋯O and C—H⋯O interactions and by π–π stacking interactions of the inversion-related naphthalene units [centroid–centroid distance of 3.7373 (14) Å].