Photocatalytic degradation has gained attraction in the self-cleaning construction materials applications because of its ability to be used to protect surface of cementitious materials and minimize the negative effects of environmental conditions on building, and to remove the dyes and other organic pollutants from water and wastewater. In this study, the influence of nano-Ceria particles on the photocatalytic degradation of methylene blue dye of cement mortar samples was investigated. In this work, nanoceria was prepared via simple co-precipitation method. Nanoceria is a powerful photocatalyst due to its high visible-light absorptivity, strong redox ability, high oxygen storage/release capacity, eco-friendly nature, photostability and cost effectiveness. Nano ceria showed a photocatalytic and self-cleaning activity in the presence of sun radiation. Nano ceria particles were characterized by X-ray diffraction, High resolution transmission electron microscope, and Ultra-violet visible spectroscopy. The presence of active oxygen species detected on nano- ceria surface was identified as cause of the photobleaching of dyes in presence of UV-irradiated.