Oxidative stress is associated with postmenopause and is also responsible for various metabolic alterations. The redox imbalance observed during ovarian decline can be induced experimentally by bilateral ovariectomy in rats. In addition to hormone replacement, regular moderate physical exercise is indicated to prevent several common postmenopausal diseases. This study aimed to assess the effect of daily swimming on the antioxidant defense system of oophorectomized Wistar rats. Control and oophorectomized groups were submitted to 1 h of daily swimming for 90 days. Levels of lipid peroxidation and glutathione content and the activities of superoxide dismutase enzyme and glutathione peroxidase in erythrocytes, liver, and brain were assessed every 30 days. The control group exhibited lower lipoperoxidation that was associated with a significant increase in superoxide dismutase enzyme activity, glutathione peroxidase activity, and glutathione content in erythrocytes and liver; however, swimming did not cause changes in antioxidant parameters in the brain over time. The oophorectomized group showed no antioxidant adaptation to daily swimming and had greater oxidative damage in the liver and blood. Our results suggest that ovariectomy hinders antioxidant adaptation in Wistar rats submitted to daily swimming.