Lead (Pb) is a toxic heavy metal widely distributed in the environment. Recent studies suggest oxidative stress as one possible mechanism involved in Pb poisoning. The unicellular algae Chlorella vulgaris (CV) contains various bioactive substances with antioxidant for the prevention of oxidative stress by metals. We investigated the protective effects of CV on the oxidative system in five groups of male Sprague-Dawley rats fed American Institute of Nutrition (AIN)-76 diet, plus 2, 5 or 10% CV for 4 weeks. All animals were exposed to 200 mg/l lead acetate by drinking water except for the control (tap water). Body weight gains were significantly reduced in the Pb-exposed group (64%) relative to the control and CV groups. Brain weights were significantly increased in the Pb-exposed group (44%) relative to the others. In the experimental period, food intake, water intake and Pb intake were not different among the groups. The levels of Pb (87%) in brain obtained from the Pb-exposed group were significantly increased compared to the other groups. The levels of oxidative stress parameters in the brain such as superoxide dismutase (36%), glutathione peroxidase (63%), and glutathione reductase (30%) were decreased in the Pb-exposed group relative to the control but markedly increased in the CV groups. The CV also significantly increased glutathione levels by approximately 1.7-fold over the Pb-exposed group, while the malondialdehye concentration significantly decreased by approximately 47-71%. Based on these results, we found alterations in several indicators of oxidative stress of Pb intoxication, suggesting the antioxidant potential of CV. Therefore, CV may have protective effects on brain damage of low-level and short-term Pb exposure in the brains of rats.