In the title compound, C(21)H(20)N(2)O(4), the naphthalene ring system makes a dihedral angle of 84.5 (3)° with the benzene ring, and the -C(=O)-N(H)-N(H)-C(=O)- torsion angle is 70.7 (7)°, so that the mol-ecule is twisted. An S(6) ring motif is formed via an intra-molecular O-H⋯O hydrogen bond. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯O hydrogen bonds into supra-molecular layers in the ab plane.