The title compound, C(14)H(13)N(3)O(3)·H(2)O, was prepared by the reaction of 4-methoxy-salicylaldehyde and isonicotinohydrazide in ethanol. The Schiff base mol-ecule is not planar and has an E configuration with respect to the methyl-idene unit. The dihedral angle between the benzene and pyridine rings is 36.8 (2)°. In the mol-ecule there is an intra-molecular O-H⋯N hydrogen bond involving the hydroxyl substituent and the N atom of the 2-hydr-oxy-4-methoxy-benzyl-idene unit. In the crystal, the mol-ecules are linked through inter-molecular O-H⋯O, O-H⋯N and N-H⋯O hydrogen bonds, forming layers parallel to the bc plane.