The asymmetric unit of the title compound, C16H15N3O·H2O, contains an N′-(2-methyl-3-phenylallylidene)nicotinohydrazide molecule and a water solvent molecule. The dihedral angle between the pyridine ring and the phenyl ring is 47.26 (5)°. Intermolecular O—H⋯N, O—H⋯O, N—H⋯O and C—H⋯O hydrogen bonds are found in the crystal structure. Furthermore, C—H⋯π interactions involving the pyridine and phenyl rings are also found