In the title hydrated hydrazine compound, C12H17N3O·H2O, the C=N bond adopts an E conformation. In the crystal, water molecules bridge the hydrazine molecules, via N-H...O and O-H...O hydrogen bonds, forming sheets parallel to the bc plane. There are C-H...[pi] interactions present within the sheets, and further C-H...[pi] interactions link the sheets to form a three-dimensional structure.
Keywords: crystal structure; hydrazine; hydrogen bonding.