Synthesis and characterization of nanocomposite membranes for proton exchange membrane fuel cell (PEMFC) operating at different temperatures and humidity were investigated in this study. Recast Nafion composite membrane with ZrO2 and TiO2 nanoparticles with 75 nm in mean size diameter, prepared for PEM fuel cells. Nafion/TiO2 composite membranes have been also fabricated by in-situ sol-gel method. However, fine particles of the ZrO2 were synthesized and Nafion/ZrO2 composite membrane were produced by blending a 5% (w/w) Nafion-water dispersion with the inorganic compound. All nanocomposite membranes demonstrated higher water retention in comparison with unmodified membranes. Proton conductivity increased with increasing ZrO2 content while TiO2 additive (with mean size of 25 nm) enhanced water retention. Subsequently, structures of the membranes were investigated by Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) as well as X-Ray Diffraction (XRD). In addition, water uptake and proton conductivity of the modified membranes were also measured. The nanocomposite membrane was tested in a 25 cm(2) commercial single cell at the temperature range of 80-110 degrees C and in humidified H-2/O-2 under different relative humidity (RH) conditions. The membrane electrode assembly (MEA) prepared from Nafion/TiO2, ZrO2 presented highest PEM fuel cell performance in respect of I-V polarization under condition of 110 degrees C, 0.6 V and 30% RH and 1 atm. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.