In the crystal of the title compound, C15H13NO4·CH3OH, the Schiff base molecule exists in the zwitterionic form; an intramolecular N—H...O hydrogen bond stabilizes the molecular structure. The benzene rings are nearly co-planar, subtending a dihedral angle of 5.34 (2)°. In the crystal, classical O—H...O and weak C—H...O hydrogen bonds link the Schiff base molecules and methanol solvent molecules into a three-dimensional supramolecular architecture. The crystal studied was refined as an inversion twin.