Introduction: Diabetes mellitus is a metabolic disorder, which affects many people throughout the world. The inefficacy and multiple side effects of most synthetic anti-diabetic drugs are reported by various studies. Thus, many researchers are focused on the use of medicinal plants as safe and potent anti-hyperglycemic drugs. The aim of this study is the evaluation of the effect of Afghan senjed (Elaeagnus Angustifolia L.) leaves aqueous alcoholic extract on blood glucose level of diabetic rats. Methods: Rats were divided into 6 groups: normal, diabetic, metformin and Elaeagnus Angustifolia leaves extract (EALE) groups, which received 200, 400 and 800 mg/kg doses of extract for 15 days. Diabetes was induced by single dose intraperitoneal administration of streptozotocin (STZ). During treatment, the effect of single and repeated oral administration of EALE on blood glucose level of diabetic rats was evaluated. On last day, the effect of EALE on oral glucose tolerance test (OGTT) was also assessed. Results: All doses of EALE showed significant reduction in blood glucose level, an improvement of glucose tolerance and enhancement in body weight. Conclusion: EALE possessed an antihyperglycemic property in diabetic rats.