 Despite the recent progress in Zn-air battery fabrication, the development of highly electroactive, non-precious-metal-based, and durable electrocatalysts for such batteries remains challenging. To address this issue, spinel-type MnCo2O4.5 nanoparticles (NPs) prepared by a solvothermal method followed by calcination were characterized by a range of instrumental techniques and employed in rechargeable Zn-air batteries to promote the oxygen reduction and oxygen evolution reactions. The bifunctional activity of the MnCo2O4.5 NPs was further evaluated by linear sweep voltammetry, which showed that both the reduction and oxidation current densities obtained in the presence of this catalyst exceed those observed with catalyst-free carbon. Moreover, the incorporation of the MnCo2O4.5 NPs into an air-breathing cathode resulted in a decreased charge–discharge voltage gap and improved round-trip efficiency. Therefore, these MnCo2O4.5 NPs are a highly beneficial and novel kind of bifunctional electrocatalyst for rechargeable Zn-air batteries.