||Recent development in mobile electronic devices and electric vehicles requires electrical wires with reduced weight as well as enhanced stability. In addition, since electric energy is mostly generated from power plants located far from its consuming places, the mechanically stronger and higher electric power transmission cables are strongly demanded. However, there has been no alternative materials that can practically replace copper materials. Here, we report a method to prepare ultra-strong carbon-Cu core-shell wires with significantly enhanced electrical and mechanical properties. The core carbon nano-material based fibers (CFs) are synthesized by chemical vapor deposition (CVD), followed by electroplating of Cu shells, where the large surface area of CFs in contact with Cu maximizes the mechanical toughness of the cores-shell wires. At the same time, the unique electrical and thermal characteristics of graphene allows ~10 times higher current density limit, providing more efficient and reliable delivery of electrical energies through the CFs-Cu wires. We believe that our results would be useful to overcome the current limit in electrical wires and cables for light-weight, energy-saving and high-power applications.