Palladium (Pd)-based anode catalysts show greater activities than Pt catalysts for HCOOH oxidation. However, because of the ease of Pd oxidation, the electrocatalytic stability of Pd is not satisfactory. In the present study, 2.4-wt% Pd supported on N-functionalized carbon nanotubes (Pd/NCNTs) with high dispersion areas and narrow size distributions exhibited superior HCOOH-oxidation performance in comparison to Pd on charcoal (commercial Pd/C, 30-wt% Pd) and Pd on HNO3-treated CNTs (Pd/OCNTs). Surface characterization revealed that the interactions between Pd nanoparticles (PdNPs) and surface N-functionalities optimized local structures of the PdNPs and participated in the HCOOH oxidation by influencing the electronic properties of the PdNPs. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.