We demonstrate a simple method for enhancing the electrochemical performance of air electrodes of Li–air batteries using a polydopamine coating on the surface of carbon. A thin polydopamine layer on Ketjen black carbon clearly modified the surface properties of the air electrode, in turn resulting in improved electrolyte filling. The coating also passivates surface carbon defects, which may be helpful in suppressing parasitic reactions during cycling. Electrochemical tests of the electrode indicate that the introduction of the polydopamine layer is beneficial in that it increases the capacity, lowers the overpotential, and improves the cyclic performance of Li–air cells. These effects may be associated with the increased active catalytic area of the electrode, mostly resulting from the improved wetting characteristics. The suppression of parasitic reactions due to the passivation of carbon defects also contributes to the enhanced cyclic performance of the polydopamine-treated electrode.