This article reports a detailed reinvestigation of the reaction of bis(dialkyldithiocarbamato)zinc(II) (ZDAC) with amines. The reaction of primary amines with bis(dimethyldithiocarbamato)zinc(II) (ZDMC) results in the formation of a 1,1,3-trisubstituted thiourea, a 1,3-disubstituted thiourea, dimethylammonium dimethyldithiocarbamate (DMADC), ZnS, and H2S. The ratio of formation between the two thiourea products strongly depends on the reaction conditions chosen. A new mechanism is proposed, which involves the formation of an amine-dithiocarbamic intermediate, from which the two most important products, a 1,1,3-trisubstituted and a 1,3-disubstituted thiourea, are formed. Also, direct transformation of the 1,1,3-trisubstituted thiourea into the 1,3-disubstituted thiourea via nucleophilic attack of the primary amine onto the thiocarboxy of the 1,1,3-trisubstituted thiourea was found to occur, catalyzed by ZnCl2. The reaction of primary amines with ZDACs is catalyzed by elemental sulfur, which has been attributed to sulfur insertion in the zinc-ligand ring of the ZDAC, resulting in a higher reactivity of the ZDAC complex. Finally, when ZDACs are reacted with a secondary amine, no thiourea products are formed and only a mixture of zinc dithiocarbamates is obtained.