The title compound, C6H7N2O2 +·Br−, is isomorphous with 2-nitro­anilinium chloride and contains an characteristic intra­molecular N—H⋯O hydrogen bond, forming an S(6) motif. Inter­molecular N—H⋯Br hydrogen bonds occur in the crystal structure. Two zigzag chains of C 2 1(4) motifs extend along the b-axis direction. These primary chain motifs inter­sect like a double helix structure, leading to R 6 3(12) ring motifs, which are arranged in tandem along the b axis. Hence, hydro­philic layers are generated at z = 1/4 and 3/4, which are sandwiched between alternate hydro­phobic layers across z = 0 and 1/2.