Nanostructured Mo2C/CNTs composites have been synthesized by using a novel methodology of microwave-assisted thermolytic molecular precursor with Mo(CO)(6) as single source precursor. Pt electrocatalysts supported on the Mo2C/CNTs composites were prepared by using the modified ethylene glycol method. The resulting Mo2C/CNTs and Pt-Mo2C/CNTs were characterized by inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis, X-ray diffraction, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The rotating disk electrode experiments were used to measure electrocatalytic activity for oxygen reduction reaction. The results showed highly dispersed sphere-like Mo2C and Pt particles with 3-6 nm can be prepared upon CNTs by the above-mentioned methods. The formation process of Mo2C includes the following steps: decomposition of Mo(CO)(6) precursor to the metallic Mo and CO, CO dismutation reaction, formation of the MoOxCy by the metallic Mo and CO, the MoOxCy carburization to Mo2C, and further carburization of Mo2C to Mo3C2. The Pt-Mo2C/CNTs sample gave higher electrochemical surface area and activity for oxygen reduction reaction with a more positive onset potential in acid solution than those of Pt/CNTs under the same condition, which was attributed to the synergistic effect among Pt, Mo2C, and CNTs. The findings indicate that Mo,C is an inexpensive and promising alternative to precious metal and worthy of further exploring for other applications in catalysis.