In the title compound, C19H15N3O2·H2O, the oxa-diazole ring and the quinoline unit are almost coplanar, making a dihedral angle of 7.66 (8)°. The dihedral angle between the benzene ring and the quinoline system is 25.95 (8)° while that between the benzene and the oxa-diazole rings is 18.88 (9)°. The water mol-ecule is hydrogen bonded to an oxa-diazole N atom and to the quinoline N atom. In the crystal, these units are linked via C-H⋯O hydrogen bonds, forming two-dimensional net-works lying parallel to the ab plane.