Studying the influence of gamma (γ) -rays processing on the anti-oxidant activity of chard (Beta vulgaris) leaves and implementing of the conceivable hypo-lipidemic and anti-oxidant potential of aqueous extract of γ-irradiated chard leaves (GCLAE) against high fat diet (HFD) were the two objectives of this study. Processing of dried chard leaves by γ-rays (10 kGy) caused a significant elevation in the total phenolic content, total flavonoids, and antioxidant activity compared to the raw samples. Data showed that feeding rats HFD for 10 weeks induced a state of dyslipidemia, increase the levels of inflammatory factors, liver and cardiac markers, and also induced the level of lipid peroxidation with significant depletion of the antioxidant status relative to the control group. Supplementation of GCLAE along with HFD resulted in remarkable protection against HFD-complications and that is evidenced by reduction in total cholesterol (TC), triglycerides (TG), Low-density lipoprotein-cholesterol (LDL-C) and very Low-density lipoprotein-cholesterol(VLDL-C), remarkable increase in high-density lipoprotein cholesterol (HDL-C), tumor necrotic factor-alpha, interleukin-6, decrease the level of liver and cardiac enzymes, and also GCLAE administration enhance the activity of hepatic and cardiac antioxidant parameters (glutathione content, superoxide dismutase and catalase) and reduce the level of malondialdehyde compared to rats fed HFD. Thus, it could be concluded that γ-irradiation technique might be useful for chard processing with the purpose of shelf-life prolongation as well as to increase its antioxidant capacity. Moreover, the results concluded that GCLAE may have an effective role in reducing the health complications for those fed high fat diet.