In the title compound, C(21)H(18)N(6)·H(2)O, two 4,4'-dipyridyl-amine groups are linked by a methyl-ene C atom, which sits on a twofold axis. The lattice water mol-ecule is located slightly off a twofold axis, and is therefore disordered over two positions. In the crystal, the organic mol-ecules and the water mol-ecule are linked by O-H⋯N hydrogen bonds. The organic mol-ecules exhibit extensive offset face-to-face π-π inter-actions to symmetry equivalents [centroid-centroid distances = 3.725 (3) and 4.059 (3) Å].