Phytotherapy has been achieved to maintain glycemic control in patients with diabetes mellitus. The present study was conducted to evaluate the antihyperglycemic properties of the Juglans regia leaf extract in streptozotocinnicotinamide induced diabetic rats. Nicotinamide was injected intraperitonealy (ip) 15 min before the injection of Streptozotocin (ip). One week after induction of diabetes, oral treatment started with extract of Juglans regia and Metformin and continued for 4 weeks. Fasting blood sugar, body weight, serum lipids and insulin level were measured in different groups. A significant reduction of glucose, HbA1c, total cholesterol and serum triglycerides were detected after 4 weeks in rats treated with Juglans regia leaves compared to the control groups. Thus, Juglans regia extract treatment showed potential hypoglycemic and hypolipidemic effects in type 2 diabetic rats.