A successful synthesis of Cu2ZnxSnySe1+x+2y (CZTSe) nanoparticles is presented. Nearly monodisperse and highly faceted CZTSe nanoparticles were prepared through reaction of metal amino complexes with saturated solutions of selenium in trioctylphosphine at high temperature. High-resolution transmission electron microscopy and X-ray diffraction analysis showed the prepared nanocrystals to have the tetragonal Cu2ZnSnSe4 crystallographic structure. Nanoscale-resolved electron energy loss spectroscopy images showed the presence of the four elements in each individual nanocrystal. Further analyses of the particles' chemical composition showed the nanocrystals to be consistently Zn- and Sn-poor.