The fate and impact of cerium oxide nanoparticles (CeO2NPs) on soil-grown plants have been intensively studied. However, all previous studies were performed in freshly prepared soils, without considering the temporal changes of the properties of CeO2NPs in the environment. A growing body of evidence suggests that the properties of CeO2NPs will change with aging, and therefore, it is essential to understand how the aging process affects the fate and bioavailability of CeO2NPs in the environment. In this study, the effects of aging on the fractionation of CeO2NPs in a silty loam soil and their bioavailability to radish were investigated. The results indicated that aging for 7 months did not affect the fractionation of CeO2NPs in soil. However, the aging process significantly increased the concentration of Ce3+ in soil. The soil with aged CeO2NPs contained a 40.5% higher concentration of Ce3+ than soil with fresh CeO2NPs. The aging process also resulted in a significantly higher Ce concentration in the radish shoots (87.1% higher) grown in aged soil than in freshly contaminated soil, even though the Ce concentrations in radish storage root and fine roots were comparable between plants grown in these soils. The radish growth and nutritional status were unaffected by either the fresh or the aged CeO2NPs. This study provides the first comprehensive evaluation of the effects of aging of CeO2NPs on their fate and impact on soil-grown plants.