The paper presents the synthesis of CeF3 nanoparticles from polyisobutene-butanediimede (T154)/cyclohexane/water microemulsions. The CeF3 nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffractometer (XRD) and dynamic laser light scattering (DLS). The results showed that the nanoparticles in shape, size and size distribution were strongly affected by water content and precursor concentration. With increasing water content and precursor concentration, the size and polydispersity of particles increased and the morphology of the particles was converted from the mixtures of spherical and cylindrical particles to the mixtures of cylindrical and polygonal particles. The crystal structure of nanoparticles was a face-centered cubic lattice.