The title compound, C(15)H(16)N(2)O(2)·H(2)O, was synthesized via the alkyl-ation of 3-hydroxy-methyl-idene-2,3-dihydro-1H-pyrrolo[2,1-b]quinazolin-9-one with n-propyl iodide in the presence of sodium hydroxide. The organic mol-ecule and the water mol-ecule both lie on a crystallographic mirror plane. In the crystal structure, inter-molecular O-H⋯O and O-H⋯N hydrogen bonds link the components into extended chains along [100].