In the zwitterionic title compound, C(16)H(12)N(2)O, the dihedral angle between the benzene ring and naphthalene ring system is 2.0 (1)°. The azo group adopts a trans configuration and an intra-molecular N-H⋯O hydrogen bond is found. In the crystal, the mol-ecules are packed by strong π-π inter-actions [centroid-centroid distance between aromatic rings = 3.375 (3) Å].