The title compound, C(19)H(12)N(2)O(3), has two independent mol-ecules (A and B) in the asymmetric unit. There is an intra-molecular O-H⋯N hydrogen bond in each mol-ecule. The mean planes of the naphthalene [maximum deviations = 0.024 (3) and 0.030 (3) Å in A and B, respectively] and the isoindoline units [maximum deviations 0.009 (3) and 0.008 (3) Å in A and B, respectively] are almostly coplanar, with dihedral angles of 4.25 (9) ad 3.84 (9)° in mol-ecules A and B, respectively. The two independent mol-ecules are connected by π-π inter-actions [centroid-centroid distances 3.5527 (19) and 3.5627 (19) Å]. In the crystal, the A+B pairs are further connected via π-π inter-actions [centroid-centroid distances = 3.693 (2)-3.831 (2) Å], leading to the formation of columns propagating along the a-axis direction. The columns are linked via C-H⋯O inter-actions, leading to the formation of a three-dimensional network.