Medicinal plants as a folk medicine are used for the treatment of diabetes all over the world. The Present study investigated, the effects of some indigenous medicinal plants viz Olea europea, Azadirachta indica and Trigonella foenum-graecum in terms of their antidiabetic activity such as hypoglycemic effect and improvement of body weight gain in Streptozotocin induced diabetic rats and compared with that of a patent drug as Glibenclamide.The blood glucose lowering activity of these selected plants was studied in Streptozotocin (50mg/kg, i.p.) induced diabetic rat, following oral administration of Olea europea, Azadirachta indica and Trigonella • foenum-graecum at the dose rate of 1 gm/kg, 500mg/kg and 1 gm/kg body weight respectively. Blood glucose level and body weight gain were measured by Glucotrend Kit and Electric balance respectively and that compared with a patent drug Glibenclamide at dose rate of 800pg/kg body weight. The data were compared statistically by using Student's unpaired t-test. The herbal preparations of these plants significantly reduce blood glucose level in Streptozotocin induced diabetic rats and comparable with that of the standard drug, Glibenclamide. The herbal, preparation also significantly increased body weight gain as compared with the patent drug. The present study clearly indicated the significant antidiabetic activity of Olea europea, Azadirachta indica and Trigonella foenum-graecum and supports the traditional usage of the herbal Preparations by Ayurvedic physicians for the therapy of diabetes.