Anodic co-deposition process was performed at 25 °C in the mixed manganese acetate and cobalt acetate aqueous solution to prepared binary Mn-Co oxide films. It was found that the Co content ratio in the binary oxide can be easily controlled by adjusting the composition of the plating solution. The deposited oxide showed a nanocrystalline characteristic and revealed a uniform distribution of the constituent elements, i.e., Mn, Co, and O. The experimental data also indicated that the incorporated Co effectively inhibited the irreversible anodic dissolution of the deposited oxide during cyclic voltammetric scans which were performed in aqueous KCl electrolyte; and therefore, it resulted in a great improvement in electrochemical stability of the oxide electrode. Moreover, an appropriate amount of Co oxide addition was confirmed to enhance the high rate charge-discharge capability of the binary oxide electrode. However, a high Co content (>15 wt.%) would render the formation of oxide blocks, instead of the fibrous morphology observed on the low Co content specimens, and cause a significant reduction in the specific capacitance of the oxide.