In the title compound, C(15)H(12)N(4)·H(2)O, the organic mol-ecule displays approximate non-crystallographic twofold symmetry: the dihedral angle between the benzimidazole ring systems is 81.37 (12)°. In the crystal, the components are linked by O-H⋯N hydrogen bonds, forming chains propagating in [101]. Aromatic π-π stacking [centroid-centroid separation = 3.595 (2) Å] helps to consolidate the structure.