Saud Alarifi, Daoud Ali, Saad Alkahtani Department of Zoology, College of Science, King Saud University, Riyadh, Saudi Arabia Abstract: Alumina nanoparticles (Al2O3NPs) are gradually used in various areas, including nanomedicine, biosensors, and electronics. The current study aimed to explore the DNA damage and cytotoxicity due to Al2O3NPs on human hepatocarcinoma cells (HepG2). The MTT and neutral red uptake assays showed that Al2O3NPs induce significant cell death in a dose- and time-dependent manner. However, Al2O3NPs induced significant intracellular reactive oxygen species production and elevated lipid peroxidation and superoxide dismutase levels in the HepG2 cells. Al2O3NPs also induced significant decrease in reduced glutathione levels and increase caspase-3 activity in HepG2 cells. DNA fragmentation analysis using the alkaline single-cell gel electrophoresis showed that Al2O3NPs cause genotoxicity in dose- and time-dependent manner. However, they induce reactive oxygen species production and oxidative stress, leading to oxidative DNA damage, a probable mechanism of genotoxicity. This study warrants more careful assessment of Al2O3NPs before their industrial application. Keywords: HepG2 cells, Al2O3NPs, oxidative stress, MTT assay, DNA damage