An integrated platinum/carbon nanotube (CNT)-based electrode for proton exchange membrane fuel cells has been efficiently fabricated by the in situ growth of a CNT layer onto carbon paper and by a subsequent direct sputter deposition of a Pt catalyst. Scanning electron microscopy and Raman spectroscopy demonstrated that the CNTs directly grown onto carbon paper formed a dense CNT layer with high surface roughness and porosity. Transmission electron microscopy micrographs indicated that this Pt/CNT composite catalyst consists of numerous Pt nanoparticles that are uniformly dispersed on the CNT surface without any surface oxidation treatment. X-ray photoelectron spectroscopy analysis revealed that the sputter-deposited Pt catalysts are mainly in a pure metallic state with an extremely low oxide formation. Compared with the carbon-black-based electrode with commercial Pt/VXC72R catalysts, the Pt/CNT/carbon-paper-based electrode has shown a pronounced improvement in electrochemical activity and stability, verified by polarization performance tests and in situ accelerated degradation tests. In situ cyclic voltammetry measurements further confirmed that the integrated Pt/CNT catalyst could give rise to a higher Pt utilization and a better corrosion resistance at the cathode.