Exploration of semiconductors in the field of photocatalysis plays a crucial role in energy and environmental remediation in particular oxidation/reduction of toxic organic contaminants from water and wastewater. The present research work aims on synthesis of pristine CeO2nanoparticles by precipitation method and was thoroughly characterized by Fourier Transform Infrared spectroscopy, X-ray Diffraction, UV-vis-Diffuse Reflectance Spectroscopy, High Resolution Scanning Electron Microscopy, EDAX and Electron Spin Resonance techniques. The band gap energy (Ebg) was found to be 3.19 eV. The synthesized nanomaterials showed spherical morphology and the particles size ranged from 50-93 nm. The insitu generation of ·OH radicals was confirmed from ESR studies. The synthesized CeO2nanospheres was evaluatedin photocatalytic oxidation of an azo dye Acid orange 10 under Ultraviolet and visible light irradiations. Experimental studies such as pH, catalyst amount and effect of initial dye concentration were also studied. Kinetic studies indicate the photo reaction follows pseudo-first order rate equation. The photocatalytic oxidation of dye molecules were monitored by UV-visible spectroscopy and COD analyses. The level of chemical oxygen demand (COD) of the photodegraded samples decreases in both the photocatalytic systems indicating that dye molecules readily degraded under present experimental conditions.Effect of electrolytes like MgSO4,KCl, Na2CO3 and NaHCO3 were also investigated to check interference of inorganic anions on photocatalytic oxidation of dye molecules using CeO2 nanospheres. Finally, the prepared catalyst was checked for its reusability and the photocatalyst exhibited better photocatalytic activity evenafter three cycles of regeneration.Copyright © VBRI Press.