There are two mol-ecules in the asymmetric unit of the title compound, [HgCl(2)(C(5)H(12)N(2)S)(2)]. In both mol-ecules, the N,N'-diethyl-thio-urea ligands exhibit a cis,trans geometry around their C-N amide bonds. The shapes of the mol-ecules are, to a large extent, determined by intra-molecular N-H⋯Cl hydrogen bonds formed by the N-H groups from the cis amide groups. In one mol-ecule, these groups are involved in three-center hydrogen bonds involving both chloride ligands, whereas in the other mol-ecule only one Cl ligand takes part in intra-molecular hydrogen bonding. The coordination around the Hg atom is distorted tetra-hedral with an S(2)Cl(2) donor set. Inter-molecular hydrogen bonds between N-H groups from the trans amide units of the thio-amide ligands and the chloride ligands connect the mol-ecules into a polymeric chain extending along the c axis. One of the ethyl groups of the N,N'-diethyl-thio-urea ligands is disordered over two positions in one of the mol-ecules, with an occupancy of 0.654 (17) for the major component.