Poly-(3,4-ethylenedioxythiophene)/graphene oxide/cobalt oxide (PEDOT/GO/Co3O4) nanocomposite was prepared using a single-step electropolymerization technique via chronoamperometry at 1.2V. Field emission scanning electron microscopy (FESEM) images revealed the presence of Co3O4 nanoparticles on the wrinkled-sheets of PEDOT/GO. The presence of Co3O4 particles in the ternary nanocomposite was proven using Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Ternary PEDOT/GO/Co3O4 nanocomposite electrode displayed better capacitive performances than pure PEDOT and hybrid PEDOT/GO nanocomposite. The ternary nanocomposite electrode exhibited a specific capacitance of 535.60Fg−1 and excellent cycle stability with the capacitance retention of 92.69% after 2000 cycles. PEDOT/GO/Co3O4 possessed much smallest charge transfer resistance (R ct) and equivalent series resistance (ESR) indicating that the ternary nanocomposite has low charge transfer resistance and excellent electronic conductivity. Thus, PEDOT/GO/Co3O4 could be recommended as an excellent electrode material for high-performance supercapacitor.