In the title compound, C(8)H(7)N(3)O(2)·H(2)O, the 2-methyl-5-nitro-1H-benzimidazole mol-ecule, excluding the methyl H atoms, is approximately planar, with a maximum deviation of 0.137 (1) Å. The crystal structure is stabilized by water mol-ecules via N-H⋯O(water), O(water)-H⋯O and O(water)-H⋯N hydrogen bonds, forming sheets parallel to the (100) plane. A short inter-molecular contact between the benzene and imidazole rings, with a centroid-centroid distance of 3.6419 (10) Å, indicates a π-π inter-action.