The current research aimed for the fabrication of the cerium oxide nanoparticles using precipitation method and the as-fabricated sample was annealed at 400°C for 2 h. The fabricated sample was investigated using thermogravimetric analysis-differential thermal analysis, Fourier transform infrared, X-ray diffraction (XRD), field emission scanning electron microscopy, and high-resolution transmission electron microscopy. The extracted data from XRD showed that the annealed cerium oxide is in the nano-sized. The determined crystallite size equals 4.75 nm. The adsorption factors of naphthol green B dye (NGB) over the calcined CeO2 were studied using a batch method. The adsorption capacity of the NGB dye over the fabricated CeO2 nanoparticles (CEP4 sample) reaches 41 mg/g. Additionally, Langmuir adsorption isotherm and the pseudo-first-order kinetic models have utilized for the explanation of the adsorption process. Besides, the determined thermodynamics factors of the separation process showed spontaneous, physisorption, and endothermic process.