Three types of composite supercapacitor electrodes were prepared; electroactive polyaniline (PANI), PANI/multi-walled carbon nanotube (CNT), and PANI/CNT/RuO2. Specifically, the PANI and PANI/CNT were prepared by polymerization, and PANI/CNT/RuO2 was prepared by electrochemical deposition of RuO2 on the PANI/CNT matrix. Cyclic voltammetry between −0.2 and 0.8 V (vs. Ag/AgCl) at various scan rates was performed to investigate the supercapacitive properties in an electrolyte solution of 1.0 M H2SO4. The PANI/CNT/RuO2 electrode showed the highest specific capacitance at all scan rates (e.g., 441 and 392 F g−1 at 100 and 1,000 mV s−1, respectively). In contrast, the PANI/CNT electrode demonstrated the best capacitance retention (66%) after 104 cycles. Additional analysis including morphology and complex impedance spectroscopy suggested that with small loading of RuO2, an increase in capacitance was observed, but dissolution and/or detachment of RuO2 species from the electrode might occur during cycling to reduce the cycle performance.