Ga-doped AgIn5S8 films are grown on indium-tin-oxide-coated glass substrates using chemical bath deposition. The structural, optical, and photoelectrochemical properties of the samples are investigated as a function of the [Ga]/[(Ga+In)] molar ratio in the precursor solution. X-ray diffraction pattern of a cubic AgIn5S8 phase appears for the undoped sample. With increasing [Ga]/[(Ga+In)] molar ratio in the precursor solution, the diffraction peaks of the samples shift to higher angles. Images from a scanning electron microscope reveal a change in the microstructures of samples from diamond-like to plate-like with an increase in Ga3+ ions in the precursor solution. The thicknesses and direct and indirect band gaps of the samples, determined from surface profile measurements and transmittance and reflectance spectra, are in the ranges of 672-275 nm, 1.91-1.85 eV and 1.68-1.50 eV, respectively. The maximum photoelectrochemical response of samples in K2SO3 (0.25 M) and Na2S (0.35 M) aqueous solution reaches 2.3 mAcm(-2) at an external potential of + 1.0 V vs. an Ag/AgCl reference electrode under illumination using a 300-W Xe lamp. The experimental results show that Ga doping with an [Ga]/[(Ga+In)] molar ratio of 0.02 improves the performance of the AgIn5S8 photoabsorber for photoelectrochemical applications. Crown Copyright (C) 2012 Published by Elsevier B. V. All rights reserved.