Exercise is known to increase free fatty acid and glucose metabolism. In consideration of such physiological effects of leptin such as reducing food intake and increasing energy consumption, many researchers have studied the relation between leptin and exercise. Despite the inconsistency between results, it is generally accepted that physical activity causes changes in leptin secretion. The present study aims to determine the changes that occur in plasma leptin levels of the rats subjected to acute swimming exercise, immediately after exercise, and in the 24th and 48th hours following exercise. Forty adult male rats of Spraque Dawley species were equally allocated to 4 groups. Group 1: General Control Group. Group 2: Swimming Group, the group that was decapitated just after 30-minutes of acute swimming exercise. Group 3: Swimming Group, the group that was decapitated 24 hours after 30-minutes of acute swimming exercise. Group 4: Swimming Group, the group that was decapitated 48 hours after 30-minutes of acute swimming exercise. Plasma leptin levels of the experimental animals were determined according to RIA method in the blood samples collected by decapitation method. Comparison of plasma leptin levels between groups revealed that the Group 3 had the highest plasma leptin levels (p <0.01). Plasma leptin levels in the Group 1 (control) and 4 were not different and the Group 2 had the lowest plasma leptin levels (p <0.01). Results of the present study show that an acute swimming exercise and/or stress factors associated with an acute exercise inhibit leptin secretion from the adipose tissue.