A photoelectrochemical study of Cu(In ,Ga)Se 2 (CIGS) thin films in 0.5 M H 2SO 4 is presented in this work. CIGS thin films were obtained by electrodeposition of CuInSe 2 (CIS) and the composition was adjusted by physical vapor deposition (PVD) to obtain CuIn 1− x Ga x Se 2. Photo-electrodes were prepared using CIGS thin films. These electrodes exhibited cathodic photoresponse associated with the hydrogen evolution occurring at 0.3 V more positive potential than the potential observed for the hydrogen evolution in the dark. The production of hydrogen by CIGS films at different potentials was estimated by coulometric measurements, showing that under illumination the quantity of hydrogen produced was two orders of magnitude higher than the hydrogen produced in the dark.