The objective of this work was to assess on antioxidant status of rat plasma, liver and adipose tissue the influence of ethanolic extract of Sargassum wightii (SWEE) under conditions of Obesity induced by dietary fructose. SWEE at 500 mg kg−1 of body weight was administered for 8 weeks toWistar rats that were fed with a High fructose diet (HFD). The Body weight of the rats was determined and Plasma, Liver and Adipose tissue was isolated to determine oxidative stress markers [malondialdehyde (MDA), reduced glutathione (GSH)], antioxidant enzymes [superoxidedismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)] activity and vitamin-C and vitamin-E activities. The concentration of MDA was significantly higher in HFD fed rats, as compared to control animals.Conversely, SOD, CAT and GPx, GSH, vitamin-C and vitamin-E content in HFD fed animals showed a significant decline when compared with control. The administration of SWEE to the rats reduced the body weight and the activities of these antioxidant factors attained a near-normalcy. Different compounds found in the SWEE explain the regulating effect over different antioxidant status that protects the animals fed a high fructose diet (HFD) against the production of free radicals.