The title compound, C(18)H(16)BrN(3)O(4)S, is a Schiff base ligand of 5-bromo-salicylaldehyde and sulfisoxazole [or N-(3,4-dimethyl-5-isoxazol)sulfanilamide]. The present structure is a zwitterion and is a more precise reinterpretation of the structure which was originally reported by Hämäläinen, Lehtinen & Turpeinen [Arch. Pharm. (1986), 319, 415-420]. The two aromatic rings which make π-π inter-actions [centroid-centroid distance 3.7538 (18) Å] through intermolecular interactions. There is also a C-Br⋯π inter-action [3.6333 (15) Å] with the heterocyclic ring. An intra-molecular N-H⋯O hydrogen bond also exists. Dimers are formed due to inter-molecular N-H⋯O hydrogen bonding. Inter-molecular C-H⋯O hydrogen bonding links a methyl C atom and the phenolate O atom. The dimers are linked by C-H⋯N hydrogen bonds, where the C atom is from the Schiff base group and the N atom is of five-membered heterocyclic ring.