Several zinc alkyldithiocarbamates [Zn(S2CNR2)(2)] were synthesized, and their thermal decomposition in the presence of alkylamines was studied in order to understand the formation of metal sulfide nanoparticles. The major intermediates and side products were isolated under various conditions and characterized by NMR spectroscopy and LC-MS. The analysis results showed that nucleophilic attack of the metal-coordinated amine on the most electron-deficient thiocarbonyl carbon of the alkyldithiocarbamate ligands at high temperature initiated the decomposition to generate thiourea, hydrogen sulfide, and solid metal sulfide nanoparticles. From the proposed decomposition mechanism, the role of amines in thermolysis was studied, and methods for synthesizing various metal sulfide nanoparticles were generalized. Formation of the desired products was confirmed by carrying out model experiments.