A 80 mu m thick composite ion-exchange membrane was synthesized by uniformly dispersing sub-micron to nano sized silica immobilized phosphotungstic acid (Si-PWA) inorganic ion exchanger into cross-linked poly(vinyl alcohol) (PVA) matrix. ATR-IR spectrum confirmed the PVA cross-linking and presence of Si-PWA in membrane. Amorphous behavior of the membrane indicated uniform blending of crystalline Si-PWA particles with cross-linked PVA. Membrane's tensile strength (93 MPa) was much higher than Nafion 117 (34 MPa). Ion exchange capacity of the membrane (0.90 meqg(-1)) was higher than the values reported for the other PVA based membranes. Na+ transport number was 0.92, indicating good ion-selectivity of the membrane. Membrane showed a high water uptake of 35% while its methanol uptake was low (8.4%) and thereby reduced methanol permeability (1.6 x 10(-7) cm(2) s(-1)) compared to Nafion-117 was observed, a highly desirable property for DMFC application. Proton conductivity increased from 7.04 mS cm(-1) to 10.5 mS cm(-1) with increase in temperature from 30 degrees C to 50 degrees C. At 35 degrees C, the single cell DMFC with membrane showed higher OCV (0.8 V) and comparable peak power density to Nafion-117. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.