The widespread presence of textile dye pollutants as byproducts in water bodies has raised serious concerns about the impact on the environment and human health. In this study, a nanocomposite material was made and its performance as a photocatalyst was looked at under different optimal conditions. The La2O3/CeO2 nanocomposite was created at room temperature using a simple and cost-effective co-precipitation method. In this study, different characterization tools, such as XRD, FE-SEM, UV-Drs, XPS, FT-IR, PL, and EDS, were used to look at the nanoparticles' structures, shapes, and optical properties. In the photocatalytic activity investigation, methylene blue (MB) dye was employed as a chosen pollutant, and illumination was delivered by a 450-Watt mercury vapor UV lamp. The La2O3/CeO2 nanocomposite removed 93% of the methylene blue dye in 100 min, compared to pure La2O3 and CeO2 nanoparticles (NPs). When the catalyst concentration was optimized at 25 mg/L and the pH was set to 12, 93% of the methylene blue was degraded in 100 min. The recyclability studies also revealed that the La2O3/CeO2 photocatalyst maintained an 84% degradation efficiency up to the fourth cycle, indicating that it is a stable and effective catalyst. Studies that used scavengers found that hydroxyl radicals were responsible for the breakdown of MB. Thus, La2O3/CeO2 photocatalysts may be regarded as a viable option for degrading organic dye pollutants in aqueous solutions.