Nanometric ceria-decorated SBA-15 was prepared using a route involving the impregnation of SBA-15 pores by a solution of cerium(III) 2-ethylhexanoate, followed by its thermal decomposition. According to XRF analysis, the number of successive impregnation–decomposition cycles (IDC) allows control of the CeO₂/SiO₂ ratio in the final material, and also the tailoring of the nanoparticle size of the fluorite CeO₂nanoparticles supported in the SBA-15, as confirmed by XRD, Raman and UV-Vis spectroscopies. The mean pore size of the SBA-15 decreases with successive IDC, as observed by N₂ adsorption–desorption, suggesting that CeO₂ nanoparticles are located inside the SBA-15 mesopores, as confirmed by TEM and HRTEM analyses. The degree of oxygen storage capacity (OSC) was measured by the number of hydrogen uptake from the temperature programmed reduction (H₂-TPR). It was found that the value of hydrogen uptake of SBA-15 submitted to one IDC corresponds to 3344 μmol of O₂ per gram of CeO₂, whereas those of SBA-15 submitted to five and ten IDC were 1324 and 2769 μmol of O₂ per gram of CeO₂, respectively.