Cerium oxide nanoparticles (nCeO(2)) were synthesized via the hydroxide mediated approach using cerium nitrate hexahydrate and sodium hydroxide as precursors. The nanoparticle was characterized using TEM, XRD and FTIR analysis. Its toxicity at 0.1 mM and 1 mM doses was investigated using wild-type third instar larvae and adult male flies (Oregon K strain) exposed to nCeO(2) along with food for one month. Ascorbic acid (17 mM) was used as a positive control. Results from the survival assay revealed that when compared to control, both 0.1 mM and 1 mM doses were non-toxic for a period of one month, after which the 1 mM dose was more toxic than the 0.1 mM dose. Dietary administration of nCeO(2) at both the doses did not cause developmental and behavioral defects. Important biochemical parameters such as ROS generation, superoxide dismutase activity, carbohydrate and protein levels, and acetylcholinesterase activity were not significantly altered at both the doses of the nanoparticle, when compared to control. The mRNA expression of antioxidant enzymes such as catalase and superoxide dismutase also was not significantly altered in the third instar larvae that fed on nanoparticle-containing food. The results from the above studies suggest that nCeO(2) at 0.1 mM and 1 mM doses did not elicit any significant toxicity in third instar larvae and adult flies when administered for a period of one month. This study also suggests that nCeO(2) can be used as a potential anti-oxidant compound and a beneficial drug carrier in Drosophila disease models in future studies.