Background and Objectives: Physical activity energy expenditure may mediate the relationship between plasma leptin levels and worsening insulin resistance independent of adiposity. The purpose of this study was to investigate the effects of a single session of combined exercise on leptin levels and insulin resistance index in sedentary men.Methods: Ten male subjects (22.9±1.7 years) and BMI (23±1.7kg.m-2) performed a single session of combined exercise including aerobic exercise: 60-70% of their maximal oxygen consumption for 20 min, and resistance exercise: 2 sets of 10 repetitions at 70% of 1 repetition in maximum. Leptin, glucose, insulin and insulin resistance indexes were measured before and 24 h after an exercise.Results: There were significant differences for leptin (ng.ml-1) [pre, 4.97(1.44); post, 3.84(0.83)], and insulin resistance index [pre, 1.25(0.33); post, 1.02(0.16)] (p<0.05). But glucose (mmol.l-1) [pre, 4.4(0.42); post, 4.25(0.4)], and insulin concentration (UΙμ.ml-1) [pre, 5.8(0.74); post, 5.39(0.48)] had significantly no changes after 24 h post-exercise. Conclusion: This study has suggested a single session of combined exercise along with a significant change of the leptin levels can affect positively on insulin resistance index.