Dimethyl N,N'-[thiobis(methyliminocarbonyloxy)] bis-(ethanimidothiolate), C10H18N4O4S3, is an example of a sulfenylated biscarbamate insecticide. The molecule has an approximate twofold axis through the central S atom which joins the two methyliminocarbonyloxyethanimidothiolate units. One of the two arms is planar in the crystal. Semi-empirical geometry optimization for an isolated molecule favors a model with both arms planar and, thus, crystal packing may be responsible for the observed non-planarity in one arm. Bond lengths and angles have similar values to those of the 'monomeric' carbamate insecticide methomyl.