The paper presents a novel approach to fabricate yarn supercapacitors (YSCs) using coaxial wet-spinning technology to create polyelectrolyte-wrapped graphene/carbon nanotube (CNT) core-sheath fibers. These fibers are used as electrodes in two-ply YSCs, which exhibit ultra-high capacitances of 269 and 177 mF cm⁻² with energy densities of 5.91 and 3.84 μWh cm⁻², respectively, when using liquid and solid electrolytes. The combination of scalable coaxial wet-spinning and the excellent performance of YSCs paves the way for wearable and safe electronics. The authors also demonstrate the integration of these YSCs into a cloth supercapacitor, achieving a capacitance higher than that of commercial capacitors. The study highlights the potential of this approach for high-energy-density and safe wearable electronics.The paper presents a novel approach to fabricate yarn supercapacitors (YSCs) using coaxial wet-spinning technology to create polyelectrolyte-wrapped graphene/carbon nanotube (CNT) core-sheath fibers. These fibers are used as electrodes in two-ply YSCs, which exhibit ultra-high capacitances of 269 and 177 mF cm⁻² with energy densities of 5.91 and 3.84 μWh cm⁻², respectively, when using liquid and solid electrolytes. The combination of scalable coaxial wet-spinning and the excellent performance of YSCs paves the way for wearable and safe electronics. The authors also demonstrate the integration of these YSCs into a cloth supercapacitor, achieving a capacitance higher than that of commercial capacitors. The study highlights the potential of this approach for high-energy-density and safe wearable electronics.