One of the major challenges associated with fuel cells is exploring highly efficient and low-cost electrocatalysts for the oxygen reduction reaction (ORR). Herein, the feasibility of using Ti3C2 MXene nanoparticles (NPs) to enhance the electrocatalytic activity of g-C3N4 for ORR was investigated. By varying the content of Ti3C2 NPs, a series of g-C3N4/Ti3C2 heterostructures were obtained, displaying enhanced electrocatalytic activity, including a positive shift in both onset and peak potentials toward ORR, compared to the original g-C3N4 in basic solution. We attribute the improvement to the favorable electrical conductivity of well dispersed Ti3C2 MXene nanoparticles and also enhanced O-2 adsorption due to the electronic coupling effect between g-C3N4 and Ti3C2 in the heterostructures. This work demonstrates the potential of earth-abundant MXene family materials to construct low-cost and high-performance electrocatalysts.