WO3 thin film photoanodes containing different concentrations of Ag nanoparticles were synthesized by sol-gel method. Based on UV-visible spectra, presence of a surface plasmon resonance peak at 470 nm of wavelength indicated formation of silver nanoparticles in the WO3 films. According to atomic force microscopy (ATM) analysis, the highest value for surface roughness and the effective surface ratio was observed for the sample containing 2 mol% of Ag. X-ray diffraction (XRD) patterns revealed that WO3 nanocrystalline structure was formed in the monoclinic phase with the average size of about 18.2 nm while Ag nanocrystals were determined in cubic phase. X-ray photoelectron spectroscopy (XPS) showed that Ag exists in a combination of metal/oxide states on the surface. Photoresponse investigation of the synthesized films indicated that the highest photocurrent was obtained for the sample containing 2 mol% Ag with the maximum incident photon to current efficiency (IPCE) of about 20% at 360 nm wavelength. Moreover, measuring the amount of hydrogen produced during water splitting reactions verified that the highest hydrogen production rate (similar to 3 mu mol/h) was obtained for the sample with 2 mol% Ag. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.