The assembly of nearly monodisperse and highly crystalline ceria nanoparticles into highly ordered 3D mesostructures was investigated. Nanoparticle sols with the composition were fully synthesized and characterized. It was found that the micelles of these polymers have higher hydrophobic contrast between the two blocks, low sensitivity towards alcohols, and higher temperature stability. The X ray diffraction (XRD) pattern of the calcined sample shows all the characteristic reflections of the cubic CeO2. The increase in crystallite size was evident from the decrease in peak width as compared to the initial nanoparticles. The hysteresis suggested that the spherical mesopores were connected through smaller pores. The study demonstrated the block-copolymer-assisted assembly of crystalline CeO2 nanoparticles into crystalline mesoporous structures without the aid of external agents such as surface functionalization or binding agents.