Abstract: Urtica dioica L. (Stinging nettle) has already been known for a long time as a medicinal plant in the world. This histopathological and morphometrical study was conducted to determine the effects of the hydroalcoholic extract of Urtica dioica leaves on testis of streptozotocin-induced diabetic rats. Eighteen male Wistar rats were allocated to equally normal, diabetic and treatment groups. Hyperglycemia was induced by Streptozotocin (80 mg kg-1) in animals of diabetic and treatment groups. One week after STZ injection (80 mg kg-1), the rats of treatment group received the extract of U. dioica (100 mg/kg/day) IP for 28 days. After 5 weeks of study, all the rats were sacrificed and testes were removed and fixed in bouin and after tissue processing stained with H and E technique. Tubular cell disintegration, sertoli and spermatogonia cell vacuolization and decrease in sperm concentration in seminiferous tubules were seen in diabetic and treatment groups group in comparison with control. External Seminiferous Tubular Diameter (STD) and Seminiferous Epithelial Height (SEH) significantly reduced (p<0.05) in the diabetic rats compared with controls and these parameters in the treatment group were similar to diabetics animals. This study showed that hydroalcoholic extract of Urtica dioica leaves, after induction of diabetes; has no treatment effect on seminiferous tubules alterations in streptozotocin-induced diabetic rats.