In the title compound, cis-[PtCl(2)(C(5)H(13)N(3))(C(2)H(6)OS)], the four-coordinate Pt(II) atom is bonded to one N atom of the N,N,N',N'-tetra-methyl-guanidine ligand, one dimethyl sulfoxide S atom and two chloride ligands, forming a cis-square-planar geometry. The bond lengths and angles of the N-Pt-Cl functionality are typical for imine dichloridoplatinum(II) complexes. The H atom of the imino group is oriented towards the O atom of the sulfoxide group of a neighboring mol-ecule and forms an N-H⋯O hydrogen bond.