The induced co-deposition mechanism in one-step electrodeposition of Cu2-xSe and CuInSe2 thin films was investigated. Cu2-xSe and CuInSe2 thin films were deposited potentiostatically on Mo substrates by a one-step process from an acidic electrolyte containing SCN- ions as complexing agents. The films were examined by scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray diffraction, and ion beam analysis methods. Good control of stoichiometry was achieved over a wide potential range, thus indicating that the film composition may indeed he controlled by the induced co-deposition mechanism. The effects of the thiocyanate ions on the reduction potentials of Cu+, In3+, and Se4+ ions were examined by cyclic voltammetry, in order to improve their crystallinity, the CuInSe2 films were annealed under a N-2 atmosphere after deposition.