Abstract Nanoparticles of copper zinc tin sulfide (CZTS, Cu 2 ZnSnS 4 ) and copper zinc tin selenide (CZTSe, Cu 2 ZnSnSe 4 ) were prepared by a synthesis route using corresponding metal salts and sulfur or selenium. Oleylamine was used as solvent and capping agent. This fast and uncomplicated preparation method delivers amine-capped nanoparticles with a diameter of approximately 7–35 nm depending on the reaction conditions, whereas CZTSe nanoparticles are bigger than similarly synthesized CZTS nanoparticles. The nanoparticles are characterized by powder-X-ray diffraction, mass spectrometry, transmission electron microscopy, high resolution transmission electron microscopy, electron diffraction and energy dispersive X-ray spectroscopy. For CZTS the chemical composition – proven by energy dispersive X-ray spectroscopy - is in good accordance with the stoichiometric chemical composition, while in the case of CZTSe the chemical composition depends strongly on the metal salts used for the synthesis. A composition close to the stoichiometric one was achieved by selecting metal salts with appropriate reactivity. Transmission electron microscopy images, as well as high resolution transmission electron microscopy images, reveal perfect crystals for the CZTS sample, in the CZTSe samples defects in the crystal structure are observed.