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).