In the title compound, C21H20N2O3, the planes of the benzene ring and the naphthalene ring system are inclined to one another by 70.95°, and by 4.99 (6) and 75.93 (5)°, respectively, to the mean plane of the pyrazoline ring. The latter has an envelope conformation with the methine (CH) C atom as the flap. There is an intramolecular O—H...N hydrogen bond that forms an S(6) ring motif. In the crystal, molecules are linked by C—H...O hydrogen bonds, forming chains along [100]. The chains are linked via C—H...N hydrogen bonds, forming sheets parallel to the ab plane. The sheets are linked by a series of N—H...π and C—H...π interactions forming a three-dimensional structure.