Developing earth abundant and highly active electrocatalysts to overcome the sluggish oxygen reduction kinetics is one of the key toward the practical applications of air batteries with economic efficiency and high energy density. Herein, a shape-controlled synthesis of mullite SmMn2O5 is achieved through a surfactant-free one-step hydrothermal method. SmMn2O5 nanoparticles (SmMn2O5-NPs) and nanorods (SmMn2O5-NRs) are successfully synthesized and in half-cell tests, SmMn2O5-NRs perform enhanced oxygen reduction activity relative to SmMn2O5-NPs in terms of a more positive half-wave potential and reduced peroxide yield. Importantly, rechargeable zinc-air batteries constructed with SmMn2O5-NRs exhibit not only higher peak power density (217 mW cm−2) over commercial Pt/C catalyst (190 mW cm−2) but also excellent cycling stability during long-term charging-discharging test over 170 h. The facile synthesis of SmMn2O5-NRs together with the remarkable electrocatalytic performance endows mullite SmMn2O5 with great promise in replacing the precious metal as future catalysts for air batteries.