Crystals of the title compound, C(16)H(12)N(2)O(4), were obtained accidentally from a hydro-thermal reaction of 5-[(1H-benzimidazol-1-yl)meth-yl]isophthalic acid with manganese bromide in the presence of N,N'-dimethyl-formamide. In the title mol-ecule, the benzimidazole ring system is almost planar, with a maximum deviation from the mean plane of 0.010 (2) Å. The benzimidazole and central benzene rings are inclined at a dihedral angle of 71.7 (6)°. The crystal structure is stabilized by O-H⋯N and O-H⋯O hydrogen bonds.