 The present study focused on a development of a buckypaper [a 45-µm-thick film composed of entangled Carbon nanotube (CNTs)] electrode or electrocatalyst support for oxygen reduction reaction (ORR). The surfaces of the pristine nanotubes in the buckypapers were functionalized by three well-known oxidative approaches: chemical, thermal, and electrochemical. Physical properties of the buckypapers and supported Pt electrocatalysts were characterized by thermogravimetric analysis, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy (TEM). Electrochemical oxidation created the highest defect density as indicated by Raman data. In contrast, no significant change in surface functional group was observed after thermal oxidation. The TEM images revealed the successful deposition of Pt particles onto the buckypapers (35 wt% Pt/CNT) by an impregnation-reduction method, with average particle size between 2.5 and 3.5 nm. Electrocatalytic activity of the Pt electrocatalysts toward oxygen reduction was evaluated using a rotating disk electrode. The ORR results showed Pt electrocatalysts supported on the modified buckypaper displayed substantially enhanced ORR activity in comparison to the pristine Pt/buckypaper. The highest ORR activity at 0.85 V was ~5.3 mA cm−2. Our results demonstrated that buckypaper may be a potential catalyst support for fuel cell applications.