In the title compound, C(11)H(11)N(2)O(2)S(+)·ClO(4) (-), the dihedral angle between the benzene and pyridinium rings is 87.33 (10)°. An intra-molecular N-H⋯O inter-action, with an S=O-bonded O atom as receptor, occurs in the cation. In the crystal structure, ion pairs occur, being linked by strong N-H⋯O hydrogen bonds. The perchlorate anion plays a further role in the mol-ecular packing by accepting several weak C-H⋯O inter-actions.