The title compound, C16H17N3O3·H2O, exists in the E conformation with respect to the azomethine C=N double bond. While the phenyl ring is almost coplanar with the central hydrazinecarboxamide group [dihedral angle = 14.18 (11)°], it is twisted slightly with respect to the other aromatic ring in the mol­ecule, with a dihedral angle of 22.88 (13)°. The packing is dominated by O—H⋯O, N—H⋯O and C—H⋯O hydrogen-bond inter­actions, forming a three-dimensional supra­molecular structure which is augmented by two types of C—H⋯π inter­actions. An intramolecular O—H⋯N interaction is also present in the molecule.

The title compound, C21H19N3O3·C3H7NO, adopts an E conformation with respect to the azomethine bond and crystallizes in the amide form. The dihedral angle between the rings lined to the C=N bond is 88.60 (12)°. The dimethyl­formamide solvent mol­ecule is disordered over two orientations with site occupancies of 0.684 (3) and 0.316 (3). The two N atoms of the hydrazinecarboxamide group are involved in inter­molecular N—H⋯O hydrogen bonds in which the dimethyl­formamide O atom acts as acceptor. The structure also features π–π inter­actions, with a centroid–centroid distance of 3.6561 (13) Å. Classical and non-classical intra­molecular O—H⋯N and C—H⋯O hydrogen bonds are also present.

(12) and 34.26 (11) Å , respectively, with the phenolic ring, the phenyl ring attached to the same C atom as the phenolic ring, and the phenylhydrazine ring. The adjacent phenolic and phenyl rings are twisted away from each other to reduce steric hindrance and make a dihedral angle of 80.59 (12) . The phenolic and phenylhydrazine rings are inclined to one another by 28.89 (11) . The rigidity of the molecule is increased by an intramolecular O-HÁ Á ÁN hydrogen bond involving the phenolic hydrogen and the azomethine N atom. In the crystal, the carbonyl O atom forms bifurcated hydrogen bonds with the two NH atoms of the hydrazinic group, leading to the formation of chains propagating along [001]. Within the chains there are also C-HÁ Á ÁO hydrogen bonds present. The chains are linked via C OÁ Á Á [3.4316 (18) Å ] and parallel slipped -interactions, involving inversion-related benzene rings [centroid-centroid distance = 3.8850 (14) Å ; inter-planar distance = 3.3895 (10) Å ; slippage = 1.899 Å ], forming sheets lying parallel to (100).