Pt nanoparticles supported on microstructure controllable carbon nanofibers (CNFs), i.e. platelet CNFs (p-CNFs), fish-bone CNFs (f-CNFs) and tubular CNFs (t-CNFs), are synthesized, and CNF microstructure effect on physio-chemical and oxygen reduction reaction (ORR) properties of Pt/CNFs is investigated. The physio-chemical properties of different Pt/CNFs electrocatalysts are characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). HRTEM results exhibit Pt nanoparticles are uniformly dispersed on CNF surface, and Pt/p-CNFs shows a smaller particle size compared with those other catalysts. XPS results reveal that CNF microstructure can influence the metal support interaction, and Pt/p-CNFs have a higher binding energy compared with Pt/t-CNFs. From cyclic voltammetric studies, it is found that Pt/p-CNFs performed a higher ORR activity than Pt/f-CNFs and Pt/t-CNFs, which may be resulted from the smaller Pt particle size and the stronger metal support interaction of Pt/p-CNFs. Furthermore, CNF microstructure can influence the reaction process. ORR on Pt/p-CNFs or Pt/f-CNFs is controlled by diffusion process, while on Pt/t-CNFs is surface reaction controlled. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.