Cerium dioxide (CeO2) nanoparticles were synthesized by a novel mechanochemical process. The precursors of Ce2(CO3)3.xH2O and NaOH were mixed at a weight ratio of 4 to 1. The mixtures were milled using a planetary ball mill with ball to powder ratio of 10:1. The products were then characterized using a battery of characterization methods, including X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and gas adsorption-desorption measurement. The as-prepared particles were largely amorphous with an average specific surface area of about 119.94 m2/g. Nanocrystalline CeO2 with crystallite size of 4.5 nm was obtained when the sample was annealed in air at 350 oC. The heat treatment results showed that the crystallinity of nanocrystalline CeO2 increased with increasing annealing temperature.