The title compound, C13H16N4O3S2H2O, crystallizes in a ‘folded’ conformation with the ester group lying over the carbamoyl moiety, with one solvent water molecule. The molecular conformation is stabilized by an intramolecular C—H  O hydrogen bond, and an N—H  O hydrogen-bonding interaction involving the lattice water molecule. The packing involves N—H  N, N—H  O, O—H  N and O—H  O hydrogen bonds and consists of tilted layers running approximately parallel to the c axis, with the ester groups on the outer sides of the layers and with channels running parallel to (101).