In the title compound, C16H14N2O4, the dihedral angle between the aromatic rings is 12.45 (6)°. The central C(=O)—N—N=C bridge is roughly planar (r.m.s. deviation = 0.0346 Å) and makes dihedral angles of 13.01 (7) and 0.56 (7)° with the attached phenyl and benzene rings, respectively. The acetic acid unit (r.m.s. deviation = 0.0066 Å) is twisted from its attached benzene ring [dihedral angle = 19.48 (6)°]. In the crystal, mol­ecules are linked by O—H⋯(O,N), N—H⋯O and C—H⋯O hydrogen bonds into sheets lying parallel to the bc plane. A weak aromatic π–π stacking inter­action is also observed [centroid–centroid distance = 3.7330 (7) Å].