In the title hydrated Schiff base, C13H12N4O3·H2O, the dihedral angle between the aromatic rings is 5.06 (11)° and an intra-molecular O-H⋯N hydrogen bond closes an S(6) ring. In the crystal, Ow-H⋯O and Ow-H⋯N (w = water) hydrogen bonds link the components... ...