CdS nanometre-sized particles have been prepared using an eco-friendly and low-cost method. This method relies on using parts of plants as reducing agents and protecting agents. Here, the synthesis of CdS nanoparticles using avocado peel extract, which converts Cd2+ to Cd atoms and then forms CdS nanoparticles, has been reported. The influence of pH, concentration of peel extract, and reaction time on the formation process of as-prepared CdS nanoparticles were studied. The structural properties of CdS nanoparticles were investigated using electron microscopic techniques (FE-SEM and TEM), and a majority of CdS particles with elongated to spherical shapes were observed. The crystalline struc- ture of CdS nanoparticles (Face Center Cubic-FCC) was confirmed using X-ray diffraction, and the particle size was estimated from the Scherrer equation at nearly 2.5 nm.