In the title salt, C(14)H(23)N(2)O(3) (+)·C(20)H(12)O(4)P(-), the dihedral angle between the two naphthyl ring systems in the anion is 57.77 (6)°. In the crystal, an O-H⋯O hydrogen bond links the components. The ammonium group engages in N-H⋯O hydrogen bonds, generating a layer structure.