Background: the traditional Peruvian medicine has been used since ancient times to Gentianaceae species for Diabetes Mellitus treatment. These include the Gentianella bicolor (Wedd.) Fabris ex JS Pringle (G. bicolor), known as "corpus huay”, “campanilla", "shashacuma", “campanilla morada ". This plant, botanically described as biennial herb, perennial, up to 60 cm tall, woody root, has been reported in the region of Cajamarca, Peru and in Bolivia between 3000 and 4500 metres above sea level. Objective: to evaluate the hypoglycemic effect of the G. bicolor aqueous extract in streptozotocin (STZ)-induced diabetic rats. Methods: in this study Twenty-eight Sprague Downley (SD) (9 weeks and weighing 200-210 g) were tested. Sprague Downley were divided into 04 experimental groups; 01 control group consisted of 07 healthy Sprague Downley and other groups consisted were STZ-induced diabetic Sprague Downley by intraperitoneal injection of Streptozotocin (60 mg/Kg B.W). A group was taken as untreated STZ-diabetic positive control SD, another STZ-induced diabetic group received glibenclamide (10 mg/kg B.W.), and the other group received the aqueous extract of G. bicolor (500 mg/Kg B.W.) daily for 21 days. Results: from day 14 of de experimentation, a significant decrease in blood glucose was observed in the experimental group treated with G. bicolor aqueous extract, showing a decrease about 40 %, 06 hours after the extract administered. The histopathological examination showed that the pancreas of STZ-diabetic SD treated with the aqueous extract of G. bicolor had a pancreatic homogeneous structure with the presence of islets virtually normal size. Conclusion: G. bicolor aqueous extract have a chronic hypoglycemic effect and a possible regenerative effect of the pancreatic islets.