In the title compound, C(9)H(10)N(4)O(2)·H(2)O, the oxime unit has an E configuration, and an intra-molecular N-H⋯N hydrogen bond results in the formation of a planar five-membered ring, which is oriented with respect to the aromatic ring at a dihedral angle of 74.82 (17)°. In the crystal structure, inter-molecular O-H⋯O and N-H⋯O hydrogen bonds link the mol-ecules and R(2) (2)(8) ring motifs are apparent.