PbS@cystine nanocrystals were synthesized mechanochemically, with lead acetate and L-cystine being used as the lead and sulfur precursors, respectively. The resulting nanocrystals are 22–34 nm in size, well-faceted and octahedral in shape. Characterization by XRD, FT-IR, NMR, FE-SEM, EDS, TEM (HRTEM) and surface area measurement methods showed that the particles are single, defect-free crystals with a high crystallinity. Furthermore, the crystals were prepared using a solvent-free procedure that was performed under ambient temperature and atmospheric pressure.