Background and aim: Oxidative stress is defined most simply as the imbalance between the production of free radicals and body ΄s antioxidant defense. Many medical plants contain natural antioxidant that can protect from biological system oxidative stress. The aim of this study was to determine the anti-oxidative stress of Nigella sativa. Methods: This quasi experimental study was performed on a group of 64 healthy subjects. They were invited to use the Nigella sativa (3mg/kg) twice a day for 14 days. The Blood samples before and after the study were measured for lipid per oxidation level (LPO) and total thiol molecules (TTM). Results: The results indicated a significant reduction of blood LPO (9.48±5.8 versus 6.74±5.65, P=0.008) and a significant increase in TTM plasma (0.26±0.17 versus 0.38±0.20, P=0.001). Conclusion: The present study reports that Nigella sativa has marked antioxidant activity therefore, it can reduce the amount of stress oxidative
