Abstract: The method for making carbon-coated copper nanoparticles is a simple, one-step for coating copper nanoparticles with a carbon shell to prevent rapid oxidation of the carbon nanoparticle core. The method involves heating or autoclaving thin sheets of copper hydroxide nitrate (Cu2(OH)3NO3) under supercritical conditions (a temperature of 300° C. and a pressure of 120 bar) for two hours. The autoclaving may be performed in the presence of an inert gas, such as argon, which may be used to remove any remaining gases, and the pressure may be released in the presence of the inert gas so that the product may be collected in the presence of air.