In the present study, Ir nanoparticles are deposited on the surface of IrO2 nanoparticles with microwave-assisted polyol process. Then the obtained Ir IrO2 nanocomposite is used as a support to prepare Pt/Ir-IrO2 nanocomposite, which has been demonstrated as an excellent bifunctional oxygen catalyst for unitized regenerative fuel cell. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), and transmission electron microscopy (TEM) characterizations indicate that ultrafine Ir nanoparticles (NPs) are uniformly dispersed on the surface of IrO2, which provides a conductive network for Pt NPs. Electrocatalytic activity and stability of Pt/Ir-IrO2 are investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and potential cycling techniques on rotating disc electrode (RDE). Results show that the electrocatalytic activity of Pt/Ir-IrO2 towards oxygen reduction reaction (ORR) is much higher than that of Pt/IrO2, and the electrocatalytic activity of Pt/Ir-IrO2 towards oxygen evolution reaction (OER) can be comparable to that of Pt/IrO2. Life tests reveal that Pt/Ir-IrO2 exhibits excellent stability. The enhanced ORR activity of Pt/Ir-IrO2 catalyst can be attributed to the improvement in electronic conductivity, and its higher stability can be assigned to the special structure, in which the interaction between Pt NPs and Ir NPs prevents Pt from agglomerating. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.