Now a days, various medicinal plants are becoming popular for the treatment of different diseases. Some medicinal plants are being used for the treatment of diabetes all over the world. The study was conducted to investigate the effects of powdered form of Stevia (Stevia rebaudiana Bertoni) leaves on blood glucose concentration and body weight in Streptozotocin induced diabetic rats and for its efficacy study with a patent drug, Glimepiride. The effects of powdered form of Stevia leaves was evaluated in the Streptozotocin (STZ; 55 mg/kg body weight as single intraperitoneal injection) induced diabetic rats and for this, powdered form of Stevia leaves was orally administered at three different dose rates of 150 mg/kg, 200 mg/Kg and 250mg/Kg body weight, respectively once a day for 3 weeks. Changes in the blood glucose levels and body weights were measured and the data obtained were compared with that of Glimepiride statistically by using Student’s unpaired t-test. The powdered form of Stevia leaves produced significant (p<0.01 or p<0.05) hypoglycemic effects on Streptozotocin induced diabetic rats in comparison with that of the standard drug, Glimepiride. Powdered form of Stevia leaves at a dose rate of 250mg/Kg decreased body weight significantly (p<0.01 or p<0.05) in STZ-induced diabetic rats. From this study, it was observed that powdered form of Stevia leaves possessed both hypoglycemic and body weight reducing effects.