Aim: One of the particular sources of oxidative stress is smoking and thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA) have been used as biomarkers of lipid peroxidation of oxidative damage. Therefore, we aimed to investigate the acute effect of moderate exercise on oxidative stress by determining serum MDA levels by TBARS in moderate smoker subjects versus non-smokers. Material & Methods: Fifty healthy subjects performing moderate intensity exercise were assigned to 2 groups as moderate smokers (11-20 cigarettes/day) (Group Smoker, n=25) and non-smokers (Group Non-Smoker, n=25). Venous blood samples were collected from all participants half an hour before exercise (pre-exercise) and immediately after exercise (post-exercise) to determine MDA levels as an indicator of lipid peroxidation in the serum by TBARS/UV (ultra violet).Results: Although no significant differences were observed in pre-exercise MDA levels between the groups, post-exercise MDA levels in smokers were significantly higher than that of non-smokers (p<0.05). Conclusion: The MDA determination in serum by TBARS/UV appears to be positively correlated with smoking status in particularly female subjects. Therefore, it can be a promising helpful tool in demonstrating the oxidative stress due to moderate exercise particularly in smokers to reorganize a healthier life style.