In the recent years, the synthesis of metal nanoparticles has received much attention due to its wide range of applications in various fields. In this study copper nanoparticles were synthesized using salmonella typhimurium. Biosynthesis of copper nanoparticles was achieved by addition of culture supernatant with aqueous copper nitrate solution (1mM). Copper nanoparticles having average diameter 49 nm have been obtained. The reaction mixture exhibit a peak at 565 nm corresponding to the Plasmon absorbance of copper nanoparticles by UV-Vis Spectroscopy. The nanoparticles were characterized by dynamic light scattering (DLS), and Scanning Electron Microscopy (SEM). The process of reduction is extracellular, which makes it an easier method for the synthesis of copper nanoparticles.