In the title compound, C18H13NO2, the naphthalene (r.m.s. deviation = 0.025 Å) and benzaldehyde (r.m.s. deviation = 0.006 Å) groups are oriented at a dihedral angle of 89.48 (4)°. The oxazine group is oriented at dihedral angles of 13.36 (4) and 85.08 (5)°, respectively, with respect to the naphthalene and benzaldehyde fragments. In the crystal, inversion dimers linked by pairs of C—HO hydrogen bonds generate R 2 2(8) loops. The dimers are linked into  chains via N—HO hydrogen bonds. Weak C—Hπ links and aromatic π–π stacking between the centroids of the naphthalene phenyl rings [centroid–centroid separation = 3.5977 (8) Å] help to consolidate the packing.