Grape seed extract (GSE) is one of the strongest known antioxidants. GSE actively prevents the formation of free radicals and assists in their elimination. Our aim was to investigate the effects on epileptiform activity of GSE administered concurrently with swimming exercises. A total of 35 male albino Wistar rats were used in this study. Epileptiform activity was induced in rats through the injection of penicillin (500 IU) into the left cerebral cortex. Thirty minutes after the application of penicillin, 200 mg/kg of GSE dissolved in normal saline was administered intraperitoneally. Based on the results of the statistical analysis, a significant decrease in spike frequency was observed after 60 minutes in the 15-minute group (67%), after 40 minutes in the 30-minute group (43%), and after 40 minutes in the 60-minute group (42%), while no significant decrease was identified in the amplitude values of the groups. According to the study results, in rats performing short-, medium-, and long-term swimming exercises, GSE administration allowed epileptiform activity to decrease within a shorter period of time. Thus, patients with epilepsy can potentially perform swimming exercises more safely by regularly using antioxidant substances.