Exploring efficient non-platinum catalysts for the oxygen reduction reaction (ORR) instead of platinum-based catalysts is vital for reducing costs of fuel cells or metal-air batteries. A Prussian blue/N-doped porous carbon (PB/NPC) nanocomposite catalyst for ORR was synthesized by a novel method of one-step high-temperature pyrolyzing the mixture of the casein extracted with ferric ions, potassium hydroxide and melamine. The PB nanocubes were embedded in the NPC, and the particle size of PB nanocubes was less than 100 nm. The presence of PB effectively reduced the production of hydrogen peroxide, and the PB/NPC catalyst exhibited high catalytic activity such as more positive onset-potential (of ∼0.93 V vs. RHE), large diffusion limiting current density (5.79 mA cm−2) close to Pt/XC-72 (20%) catalyst and good stability in alkaline media due to the stable binding structure and the synergistic effect of PB nanocubes and NPC. The synthetic strategy of the PB/NPC provides a facile and effective method for the preparation of non-platinum catalysts for energy conversion and storage applications.