Herein, a binary nanocomposite CdS/CeO₂ has been fabricated via a one-pot co-precipitation method for the degradation of Rose Bengal (RB) dye. The structure, surface morphology, composition, and surface area of the prepared composite were characterized by transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, X-ray photoelectron spectroscopy, Brunaur–Emmett–Teller analysis UV–Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The prepared CdS/CeO₂(1:1) nanocomposite has a particle size of 8.9 ± 0.3 nm and a surface area of 51.30 m²/g. All the tests indicated the agglomeration of CdS nanoparticles over the surface of CeO₂. The prepared composite showed excellent photocatalytic activity in the presence of hydrogen peroxide under solar irradiation towards the degradation of Rose Bengal. Near to about complete degradation of 190 ppm of RB dye could be achieved within 60 min under optimum conditions. The enhanced photocatalytic activity was attributed to the delayed charge recombination rate and a lower bandgap of the photocatalyst. The degradation process was found to follow pseudo-first-order kinetics with a rate constant of 0.05824 min⁻¹. The prepared sample showed excellent stability and reusability and maintained about 87% of the photocatalytic efficiency till the fifth cycle. A plausible mechanism for the degradation of the dye is also presented based on the scavenger experiments.