In the title compound, C23H19NO2, an oxazine Mannich base derivative, the oxazine ring has a half-chair conformation. The 2-hy-droxy-naphthalen-1-yl substituent is placed in an axial position. There is an intra-molecular O-H⋯N hydrogen bond, forming an S(6) graph-set motif. In the crystal, mol-ecules are connected by a pair of C-H⋯π inter-actions into an inversion dimer, which is reinforced by another pair of weak C-H⋯π inter-actions. The dimers are linked by a π-π inter-action [centroid-centroid distance = 3.6268 (17) Å], consolidating a column along the a axis. Furthermore, the columns inter-act with each other by a weak C-H⋯π inter-action, generating a three-dimensional network.