A novel and simple, visible light-activated photoelectrochemical (PEC) sensor, based on n-type cadmium telluride (CdTe) nanoparticles and reduced graphene oxide (rGO), is proposed for catechol detection for the first time. rGO films were directly deposited onto an indium tin oxide (ITO) electrode via the cyclic voltammetric reduction of graphene oxide. CdTe nanoparticles were synthesized on the rGO/ITO surface via cathodic electrodeposition. To investigate the PEC performance of the as-prepared CdTe/rGO/ITO photoelectrode, the photoelectrode was used to detect trace catechol under visible light irradiation. The sensor exhibited a wide linear range, low detection limit, and high sensitivity given the photoactivity of CdTe and the high conductivity and large surface area of the rGO. The proposed CdTe/rGO/ITO electrode successfully detected trace amounts of catechol in several real water samples. Findings suggest that CdTe/rGO/ITO electrode is a promising candidate for PEC analysis. (C) 2017 The Electrochemical Society. All rights reserved.