In the title compound, C(24)H(24)N(2)O(2), the five-membered ring of the indoline ring system adopts an envelope conformation with the spiro C atom at the flap. The dihedral angle between the benzene ring of the indoline ring system and the naphthalene ring system is 71.70 (7)°. In the crystal structure, pair of weak C-H⋯O hydrogen bonds link the mol-ecules into centrosymmetric dimers.