In the anion of the title compound, NH4 (+)·C16H13O3 (-)·2H2O, the benzene rings are twisted with respect to each other by 73.56 (10)°. In the crystal, extensive N-H⋯O and O-H⋯O hydrogen bonds link the cations, anions and lattice water mol-ecules into a three dimensional supra-molecular structure.