The synthesis of cerium dioxide (CeO2) nanopowders via mechanical solid-state reaction combined with sol–gel method was studied. Cerium(III) nitrate hexahydrate, dihydrate oxalate, NH4F, along with stearic acid or glycol, were mechanically milled. Calcination of the as-milled mixtures in air at 400 °C resulted in the formation of CeO2 nanoparticles. The dispersity and uniformity in particle size and morphology were greatly improved by both physical and chemical effects of the stearic acid or glycol brought in: on one hand, they had the space steric hindrance effect; on the other hand, they might act as complexing agents, letting the whole process being carried out in highly homogeneous dispersed circumstance. The CeO2 particles showed best dispersity and uniformity in particle size and morphology when the content of stearic acid was 20 g, along with 10 wt% NH4F. As-obtained, near spherical CeO2 particles were controlled to the size of 30–60 nm.