The title compound (3), C17H14BrN3O4S, is a Schiff base compound of 5-bromosalicylaldehyde (1) and sulfamethoxazole (2). The structure of (3) was determined by spectral (IR, H-1 and C-13 NMR), elemental analyses and X-ray diffraction data. Compound (3) crystallizes in the monoclinic space group C2/c, with a = 31.936(3), b = 6.2571(5), c = 16.903(1) angstrom, beta = 94.867(8), V = 3365.5(5) angstrom(3), Z = 8. In the molecule of compound (3), the molecule is bent at the S atom with a C-SO2-NH-C torsion angle of -86.3(3)degrees. Pairs of molecules, related by inversion centres, form intermolecular N-H center dot center dot center dot N hydrogen bonds to produce a dimer. An intramolecular phenolic O-H center dot center dot center dot N hydrogen bond is also formed. Intermolecular hydrogen bonding and pi-pi stacking hold the molecules together. The average distance between stacked benzene ring planes is 3.625(2) angstrom.