Metallic copper nanoparticles were synthesized by a bottom-up approach, andcoated with protective shells of graphene in order to get a metal nanopowder of high air stability and chemical inertness. Using an amphiphilic surfactant, a water-based copper nanocolloid could be prepared and successfully printed onto a polymer substrate by conventional ink-jet printing using household printers. The dried printed patterns exhibited strong metallic gloss and an electrical conductivity of >1Scm−1without the need for a sintering or densification step. This conductivity currently limits use in electronics to low current application or shielding and decorative effects. The high stability of graphene-coated copper nanoparticles makes them economically a most attractive alternative to silver or gold nanocolloids, and will strongly facilitate the industrial use of metal nanocolloids in consumer goods.