High performance two-ply yarn supercapacitors are fabricated by electrodeposition of transition metal oxide pseudocapacitive materials on carbon nanotube/stainless steel (CNT/SS) core spun yarns. The SS core incorporated in the carbon nanotube yarn has dramatically improved the conductivity of the substrate and the efficiency of electrodeposition of metal oxides on the electrodes. The SS core acts as current collector in the final two-ply yarn supercapacitors with significantly improved specific capacitance and up-scaled length of supercapacitors. Manganese oxide and cobalt oxide electrodeposited on as-spun CNT/SS yarn are compared for their electrochemical performance in two-ply yarn supercapacitors. Both supercapacitors displayed improvement in capacitance, energy and power densities, especially MnOx/CNT/SS yarn supercapacitor. The solid-state supercapacitor based on MnOx/CNT/SS composite yarn shows excellent electrochemical properties with a specific capacitance of 217.61 F/cm(3) at 0.02 V/s and an energy density of 4.84 mWh/cm(3) at a power density of 435.22 mW/cm(3). (C) 2016 Elsevier Ltd. All rights reserved.