Synthesis of metal nanoparticles is an exciting research area due to their wide range of application in various fields. Among metallic nanoparticles, copper (Cu) nanoparticles have attracted much attention due to their unique optical and electrical properties. Several methods (chemical, physical, and biological) have been introduced for the synthesis of these materials. In chemical reduction methods, for example, the reducing agent is a chemical solution whereas in biological ones, collection of enzymes - especially reductases fulfills this role. This review describes a brief overview of the current research worldwide on the synthesis of Cu nanoparticles.