Carbon materials have become a hot topic as potential substitutes for Pt/C catalysts for the oxygen reduction reaction (ORR). However, most of them exhibit their catalytic activities only in alkaline solutions, which severely limits their application in polyelectrolyte membrane fuel cells. To address this issue, here porous boron carbon nitride (BCN) nanosheets are fabricated by a facile and efficient polymer sol–gel method, which involves the annealing of polyvinylic akohol (PVA), boric acid, guanidine, and poly(ethylene oxide-co-propylene oxide) (P123) gel mixtures. The as-prepared porous BCN nanosheets possess a high surface area of 817 m2/g and display impressive ORR catalytic performance in both alkaline and acidic media, rivalling that of commercial Pt/C and other recently reported carbon materials. Importantly, the resulting metal-free catalysts exhibit much greater durability and higher methanol tolerance in both alkaline and acidic environments. This study provides a new insight into metal-free ORR catalysts that are practicable in industrial fuel cells.