We investigated the relation between swimming exercise and fear memory extinction. Rats that performed regular swimming exercise over six weeks underwent a fear conditioning. Twenty-eight days later, they were submitted to extinction tests. Swimming rats had enhanced extinction process throughout the 5 days of the extinction test when compared to sedentary ones (Exercise vs. Fear Conditioning vs. Test days interaction effect. This suggests that the swimming exercise accelerated the process of aversive memory extinction, reducing the expression of conditioned fear behavior. These results encourage further studies addressing the anxiolytic effects of exercise, with potential implications for anxiety disorders such as post-traumatic stress disorder.