In the structure of the title salt C(12)H(11)N(2)S(+)·I(-), the methyl-sulfanyl group of the cation is nearly coplanar with the perimidine rings, as indicated by the C-S-C-N torsion angles of 2.9 (5) and -177.2 (3)°, respectively. The (S)C-N bond lengths in the heterocyclic ring are approximately equal [1.325 (5) and 1.326 (6) Å] suggesting a degree of delocalization. In the crystal, cations and anions are linked via two discrete N-H⋯I hydrogen bonds, forming chains along the b axis.