Abstract: This study was done to determine the protective activity of the hydroalcholic extract of Urtica dioica leaves on Hyperglycemia and β-cells in hyperglycemic rats. Thirty Wistar rats were allocated in groups of normal, Diabetic and treatment. Hyperglycemia in Rats induced by 80 mg kg-1 streptozotocin. In treatment group, animals received hydroalcholic extract of Urtica dioica 100 mg kg-1 day-1 for five days, intraperitoneally and then hyperglycemia induced by streptozotocin. The blood glucose concentration was measured by using a Glucometer in 1st, 3rd and 5th weeks. In the end of 5th weeks the animals in each group were sacrificed by anesthesia and whole pancreas in three groups extracted and fixed in bouin's fluid and stained by chromealum hematoxiline-phloxine and beta cells were counted in three groups by Olympus microscope. Mean±SE of blood glucose concentrations in the end of fifth weeks were 99.4±5.0, 454.7±34.5 and 303.6±100.6 in control, diabetic and treatment groups, respectively (p<0.05). The percentages of β-cells in control, diabetic and treatment groups were 73.6, 1.9 and 22.9%, respectively. The percentage of β-cells in treatment group comparing with diabetic group was significant (p<0.05). This study showed that the protective administration of hydroalcholic extract of Urtica dioica has hypoglycemic effect and protective activity of β-cells of langerhans in hyperglycemic rats.