Recently, the study of carbon supports like carbon nanotubes (CNT) has intensified. The interaction between the support and nanoparticles improved the efficiency and durability of fuel cells (FCs), decreasing the electrocatalyst poisoning and in some cases it can modify the particle size. Palladium based nanostructured electrocatalysts, supported on glassy carbon [1], carbon black Vulcan [2] and CNT [3] are used in electrochemical energy storage devices such as FCs. In the present work, Pd and PdFe nanoparticles supported on CNT with and without functionalization (CNT and CNTox) were used for Formic Acid Oxidation Reaction (FAOR) in acid media. Electrocatalysts were synthesized by the borohydride reduction method with a metal loading of 20 wt.%. The CNTs were synthesized by the methane catalytic decomposition, and subjected to an oxidation treatment with nitric acid, named as CNTox. The morphology, composition and structural properties were studied by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) and X-Ray Diffraction (XRD). The FAOR was evaluated in acid media in a conventional three-electrode cell by means of cyclic voltammetry and chronoamperometry. From the steady state current density it was found that that Pd and PdFe supported at CNTox allowed improving the catalytic activity in comparison with the non-oxidized support as shown in Figure and Table 1. Figure 1.Potentiostatic transients of the Pd base electrocatalysts supported at CNT and CNTox at 0.4 V for 900 seconds and Table 1. Comparison of steady-state current density of synthesized electrocatalysts to the potential of 0.4 V. I.E. Espino-López, M. Romero-Romo, M.G. Montes de Oca-Yemha, P. Morales-Gil, M.T. Ramírez-Silva, J. Mostany, M. Palomar-Pardavé. Journal of The Electrochemical Society 166 (2019) D3205. L. Juárez-Marmolejo, S. Pérez-Rodríguez, M.G. Montes de Oca-Yemha, M. Palomar-Pardavé, M. Romero-Romo, A. Ezeta-Mejía, P. Morales-Gil, M.V. Martínez-Huerta, M.J. Lázaro. International Journal of Hydrogen Energy 44 (2019) 1640. H. Yan, Z. Bai, S. Chao, Q. Cui, L. Niu, L. Yang, J. Qiao, K. Jiang, Ionics 20 (2014) 259. Figure 1