In the title thio-semicarbazone derivative, C(9)H(10)N(4)OS·H(2)O, intra-molecular N-H⋯N hydrogen bonds result in the formation of two nearly coplanar five- and six-membered rings, which are also almost coplanar with the adjacent phenyl ring. The oxime group has an E configuration and is involved in inter-molecular O-H⋯O hydrogen bonding as a donor. In the crystal structure, intra-molecular O-H⋯S and N-H⋯N and inter-molecular O-H⋯O and N-H⋯S hydrogen bonds generate edge-fused R(2) (2)(8) and R(4) (1)(11) ring motifs. The hydrogen-bonded motifs are linked to each other to form a three-dimensional supra-molecular network.