This paper deals with a study on the effect of 120 MeV Ag9+ ion irradiation on photoelectrochemical properties of SrTiO3 thin films deposited on Indium doped Tin Oxide (ITO) coated glass by sol gel spin-coating technique. The structural evolution in the pristine and irradiated films was determined by X-ray diffraction and X-ray photoelectron spectroscopy. Surface morphology was studied by Atomic Force Microscopy (MM) and optical measurements were done by UV-visible absorption spectroscopy. Irradiation of SrTiO3 thin films was found to be effective in improving its photoelectrochemical properties. A noticeable decrease in the average grain diameter from 36 to 26 nm, reduction in bandgap from 3.55 to 3.43 eV and increase in roughness after irradiation contributed in enhancing photoelectrochemical activity of SrTiO3 thin films. Thin films irradiated at fluence 3 x 10(12) ions cm(-2), when used in PEC cell exhibited enhanced photocurrent of 0.16 mA cm(-2) at zero bias conditions, which was four times higher than that of the unirradiated sample. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.