In the title compound, C(15)H(13)NO(4)·H(2)O, the Schiff base exists in a zwitterionic form and a bifurcated intra-molecular N-H⋯(O,O) hydrogen bond generates two S(6) rings. The dihedral angle between the two benzene rings is 25.8 (2)°. The crystal structure is stabilized by inter-molecular O-H⋯O hydrogen bonds.