In the title compound, C11H17NO2S, the molecules interact head-to-tail through N—H⋯OS hydrogen bonds, giving discrete centrosymmetric cyclic dimers. The N—Caryl bond length [1.4225 (14) Å] is intermediate between that in N-phenyl-tert-butanesulfinamide [1.4083 (12) Å] and the N—Calkyl bond lengths in N-alkylalkanesulfinamides (1.470–1.530 Å), suggesting weaker delocalization of electrons over the N atom and the aromatic ring due to the presence of the 4-methoxy group.