In the title Schiff base compound, C(14)H(11)N(3)O(5), the dihedral angle between the two benzene rings is 1.6 (1)°. The mol-ecule displays an E configuration about the C=N bond. An intra-molecular O-H⋯O hydrogen bond is observed. In the crystal, mol-ecules are linked into layers parallel to (101) by O-H⋯O, N-H⋯O and C-H⋯O hydrogen bonds. One of the hydroxyl groups is disordered over two positions, with occupancies of 0.643 (5) and 0.357 (5).