Highly stable dispersions of copper nanoparticles with an average diameter of 80 nm were synthesized using a straightforward and cost-effective method in the presence of polyvinylpyrrolidone (PVP) as a stabilizer and without any inert gas protection. Sodium hypophosphite was used as the reducing agent in low pH value aqueous medium. The copper nanoparticles were characterized by ultraviolet-visible spectroscopy and scanning electron microscopy. The mechanism of the PVP on the stabilization of copper nanoparticles is also discussed. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013