Radiotherapy-induced toxicity is a major dose-limiting factor in anti-cancer treatment. Ionizing radiation leads to the formation of reactive oxygen and nitrogen species (ROS/RNS) that are associated with radiation-induced cell death. Investigations of biological effects of fullerenol have provided evidence for its ROS/RNS scavenger properties in vitro and radioprotective efficiency in vivo. Therefore we were interested to evaluate its radioprotective properties in vitro in the human erythroleukemia cell line. Pre-treatment of irradiated cells by fullerenol exerted statistically significant effects on cell numbers and the response of antioxidative enzymes to X-ray irradiation-induced oxidative stress in cells. Our study provides evidence that the pre-treatment with fullerenol enhanced the enzymatic activity of superoxide dismutase and glutathione peroxidase in irradiated K562 cells.