In the crystal structure of the title compound, C(18)H(17)N(3)O(3)·H(2)O, the mol-ecules are linked by O-H⋯O and O-H⋯N hydrogen bonds, resulting in a chain along the a axis. The crystal structure is stabilized by weak inter-molecular C-H⋯π (ring) hydrogen bonds and aromatic π⋯π stacking inter-actions [centroid-centroid distance = 3.902 (1) Å] between the pyrimidino rings of the quinazoline system. The tricyclic quinazoline fragment is almost planar (rms deviation = 0.0139 Å) with the two methylene C atoms of the pyrrolo ring deviating by 0.148 (2) and -0.081 (3) Å from the plane through the other atoms. The 4-nitrophenyl ring makes a dihedral angle of 12.55 (7)° with the tricyclic ring system.