Perovskite oxides have received considerable attention as useful electro-catalysts for Li-air batteries due to their properties of excellent catalytic activity, electrical conductivity, and durability. The nanostructure can enhance the electrochemical performance of perovskite oxides by enlarging the catalytic active sites. In this study, nano-size Nd0.67Sr0.33CoO3-δ (NSC) perovskite particles with a particle size of 20–50 nm and a specific surface area of 12.759 m2 g−1 were successfully synthesized by a microemulsion method. The NSC perovskite particles exhibit excellent electrocatalytic activity particularly in the oxygen evolution reaction (OER) with a high limiting current density of 33.68 mA cm-2 at 0.9 V vs. (Hg/HgO). This excellent catalytic activity can be ascribed to the existence of Co3+ and the enlarged surface area. Co3+ provides catalytically active site by forming Co3+/4+ redox couple and the enlarged surface increases active sites for reactants and catalyst particles. In this regard, nano-size NSC particles prepared by the microemulsion route provide excellent and stable electrochemical performance in the hybrid Li-air battery.