In the title compound, C(11)H(17)NO(2)S, the molecules interact head-to-tail through N-H center dot center dot center dot OS hydrogen bonds, giving discrete centrosymmetric cyclic dimers. The N-C(aryl) bond length [1.4225 (14) angstrom] is intermediate between that in N-phenyl-tert-butanesulfinamide [1.4083 (12) angstrom] and the N-C(alkyl) bond lengths in N-alkylalkanesulfinamides (1.470-1.530 angstrom), suggesting weaker delocalization of electrons over the N atom and the aromatic ring due to the presence of the 4-methoxy group.