The reactive elements (RE), such as Y, Hf, Zr and Ce (or their oxides), are added into the aluminide coatings to improve the oxidation resistance of coatings. In this work, the δ-Ni2Al3/Ni coating systems with different CeO2 contents and particle sizes were specially prepared by partially aluminizing the Ni films containing ~0, ~1, ~2 and ~3 wt. % nanometer CeO2 (15-30 nm) and ~1 wt. % micrometer CeO2 (5 μm), respectively. The effects of CeO2 contents and particle sizes on the interdiffusion of the aluminide coating and underlying substrate were investigated by annealing in vacuum at 1000 °C. The results showed that the addition of nanometer CeO2 in the δ-Ni2Al3/Ni coating system could mitigate the interdiffusion between the aluminide coating and underlying substrate and the blocking effect can be significantly improved with the increase of the CeO2 contents which is 1-3 wt. %. However, the addition of micrometer CeO2 in the coating system had little influence on the degradation of the aluminide coating. This is intrinsically correlated with the fact that the CeO2 contents and particle sizes would influence the formation of the CeO2-rich layer at aluminide/Ni film interface acting as a diffusion barrier between the aluminide coating and substrate.