In the title 1:1 co-crystal, C(10)H(7)BrN(4)S·C(7)H(5)BrO(2), the triazolothia-diazole system is approximately planar [with a maximum deviation of 0.030 (4) Å] and forms a dihedral angle of 8.6 (1)° with the bromo-phenyl ring. In the carb-oxy-lic acid mol-ecule, the carboxyl group is rotated by 6.4 (3)° out of the benzene ring plane. The crystal structure features O-H⋯N and C-H⋯O hydrogen bonds, π-π stacking inter-actions [centroid-centroid distances = 3.713 (2), 3.670 (2) and 3.859 (3) Å] and short S⋯N [2.883 (4) Å] contacts.