The title hydrate, C(10)H(10)N(4)·H(2)O, shows a small twist in the hydro-zone derivative, the dihedral angle between the pyridine and pyrrole rings being 11.08 (12)°. The pyridine and pyrrole N atoms lie to the same side of the mol-ecule being sustained in place by hydrogen-bonding inter-actions with the water mol-ecule. Further inter-molecular O-H⋯N and N-H⋯O hydrogen bonding leads to the formation of supra-molecular arrays in the ab plane.