Recently, it has been shown that an abundant material, polymeric carbon nitride, can produce hydrogen from water under visible-light irradiation in the presence of a sacrificial donor. We present herein the preparation and characterization of graphitic carbon nitride (g-C3N4) films on p-type semiconducting CuGaSe2 chalcopyrite thin-film substrates by thermal condensation of a dicyandiamide precursor under inert-gas conditions. Structural and surface morphological studies of the carbon nitride films suggest a high porosity of g-C3N4 thin films consisting of a network of nanocrystallites. Photoelectrochemical investigations show light-induced hydrogen evolution upon cathodic polarization for a wide range of proton concentrations in the aqueous electrolyte. Additionally, synchrotron radiation-based photoelectron spectroscopy has been applied to study the surface/near-surface chemical composition of the utilized g-C3N4 film photocathodes. For the first time, it has been shown that g-C3N4 films coated on p-type CuGaSe2 thin films can be successfully applied as new photoelectrochemical composite photocathodes for light-induced hydrogen evolution.