We report here for the first time on the synthesis of nanoparticles of the p-type transparent conductor LaOCuS. Nanoparticles were obtained via a solvothermal route in ethylenediamine with dehydrated lanthanum chloride (LaCl3 center dot 7H(2)O), copper monooxide, and elemental sulfur as precursors. Powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy ascertained our sample to be of high purity, while laser diffractometry evidenced a monodisperse particle size distribution centered on 126 nm. The absorption spectrum and the current potential curves recorded under chopped illumination asserted the optical transparency and the p-type electronic conductivity of our LaOCuS nanoparticles.