Ir-decorated PdCu alloy catalyst on carbon support (Ir-PdCu/C) is prepared via two-step procedure, which consists of polyol process for PdCu alloy nanoparticle supported on carbon support followed by surface replacement reaction step by Ir ions. The structure of nanoparticles is characterized by ICP-AES, XRD, and TEM-EDX. The electrochemical surface area (ECSA) and activity for oxygen reduction reaction (ORR) of Ir-PdCu/C catalyst are larger and higher than those of PdCu/C catalyst, respectively. Furthermore, Ir-PdCu/C catalysts showed a higher single cell performance as a cathode catalyst for high temperature polymer electrolyte membrane fuel cell. High electrocatalytic activities of Ir-PdCu/C catalyst could be attributed to electronic and structural modification of PdCu alloy by decoration of Ir atom selectively on the surface of PdCu alloy nanoparticle supported on carbon support, which results in PdIr alloy outer region and PdCu alloy inner region. (C) 2011 Elsevier B.V. All rights reserved.