One-pot thermos-reduction strategy was developed to prepare PdIr alloy nanoparticles (NPs) deposited on carbon nanotubes (CNTs). The obtained PdIr/CNT hybrids were characterized by transmission electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy and inductively coupled plasma-atom emission spectroscopy. The results show the dispersion of Pd NPs on CNTs can be improved by alloying with Ir, and the as-prepared PdIr NPs were uniformly deposited on CNTs with a tunable diameter from 2.3 to 4.2 nm. The electrochemical investigation exhibits Ir modification can boost the electrocatalytic activity of Pd catalysts on the formic acid oxidation with a mass current density up to 1620 mA mg(-1), which is 7.7 times that of Pd catalysts without Ir modification, and comparable to and even better than those of the Pd-based catalysts reported recently. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.