Abstract Alumina nanoparticles (NPs) are among the most important nanomaterials and are widely used in diverse areas. In this study, we evaluated the bioavailability and toxicity of alumina NPs in mice after oral exposure, compared with traditional alumina powder. Our results indicated that negligible alumina NPs were absorbed post-exposure and alumina NPs did not influence the balance of essential trace elements, including Fe, Cu and Zn. Preliminary toxicological evaluations suggested that alumina NPs were of low toxicity. The body weights were similar among the mice exposed to alumina NPs, alumina powder and 0.9% NaCl aqueous solution. The low toxicity was also indicated by the unchanged serum biochemical parameters. The implications related to the ongoing safety evaluations and applications of alumina NPs are discussed.