Methods of mitigating the effects of radiation exposure or providing a radioprotective effect in a subject are provided herein. The methods include administering a therapeutically effective amount of cerium oxide nanoparticles to the subject to mitigate the effects of radiation exposure or to offer a radioprotective effect to the subject. The cerium oxide nanoparticles are suitably less than 20 nm in diameter and have over 50% of the cerium in the 3+ oxidation state.
