The title mol­ecular salt, consists of a sulfamethoxazolium (SMZ) cation and a 3,5-di­nitro­salicylate (DNS) anion, which are linked by an N—H⋯O hydrogen bond. In the crystal, the cations and anions are linked via N—H⋯O, N—H⋯N and C—H⋯O hydrogen bonds, forming a three-dimensional framework.

In the crystal structure of the title compound, C6H10N3 +·C7H2I3O2 −·C7H3I3O2, two R 2 2(8) motifs are observed. One is generated by the inter­action of the 2-amino-4,6-dimethyl­pyrimidin-1-ium cation with the carboxyl­ate group of the 2,3,5-triiodo­benzoate anion via N—H⋯O hydrogen bonds. The other R 2 2(8) motif is formed by the inter­action of two centrosymmentrically related pyrimidine moieties through N—H⋯N hydrogen bonds. The two motifs combine to form a linear heterotetra­meric unit. Heterotetra­meric units are linked by a carbox­yl–carboxyl­ate O—H⋯O hydrogen bond (involving the O—H group of neutral 2,3,5-triiodo­benzoic acid and an O atom of the anion), forming a supra­molecular chain along the a axis. In addition, components are held by weak I⋯O interactions in the range 3.023 (5) to 3.382 (5) Å and I⋯I inter­actions in the range 3.6327 (7) to 4.0025 (8) Å.