This study presents microwave-assisted preparation of cobalt oxide (Co3O4) based nanocomposite electrodes doped with carbon dots and reduced graphene oxide. The calcination of the precursors at 400 °C for 2 h results in nanocomposites. A three-electrode cell in 2M KOH solution is used for the electrochemical measurements. The carbon dot containing electrodes enables the highest specific capacitance of 936 Fg−1 at 0.5 Ag−1 current density. Specific capacitances of pure Co3O4, and Co3O4@RGO electrodes are 448 Fg−1 and 482 Fg−1 at 0.5 Ag−1, with good rate capability even at 10 Ag−1, respectively. The cyclic stability of the electrodes is reasonably high and the electrodes retain 93%, 87%, and 88% of their initial capacitance after 10,000 cycles for Co3O4, Co3O4@RGO, and Co3O4@RGO@CDs, respectively. The optimized Co3O4@RGO@CDs electrodes were used to fabricate a symmetric supercapacitor that exhibits high specific capacitance (126 Fg−1 0.25 Ag−1) and long cycle life (%81 retention after 10,000 cycles). The fabricated supercapacitor has energy density of 17.5 Wh kg−1 and power density of 2522 W kg−1. The outstanding results demonstrate the promise of carbon dots doped transition metal oxides-based nanoparticles as promising electrodes for supercapacitor applications.