Background: Impairment of testicular function is one of complications of Diabetes mellitus (D.M) and this may result from increased oxidative stress. Vitamin E (Vit E) has antioxidant properties. Objective: To determine the microscopic changes in the diabetic testis with metformin alone or with Vit E and which of them are better to preserve the testicular structure. Materials and Methods: Fifty adult albino rats, were equally divided into five groups: Group 1: control group; group 2: diabetic group (diabetes was induced by (65 mg/kg; i.p) single dose of streptozotocin (STZ); group 3: vit.E-treated diabetic group (200 mg/kg/day) ip; group 4: Metformin-treated diabetic group (100 mg/kg/day) and group 5 Metformin and vit.E-treated diabetic group for eight weeks. Levels of testosterone, insulin and blood sugar were analyzed and testes specimens were prepared for light microscope and immunohistochemical detection of androgen receptor (AR) and caspase-3. Results: In diabetic group showed irregular seminiferous tubules with depletion, separation, vacuolation of the spermatogenic cells with perivascular and intertubular fibrosis also, the mean diameter of tubules significantly decreases. There are negative immunoexpressions of AR with positive caspase-3. Sections of metformin treated diabetic group showed incomplete or partial regeneration of germ cells while in group 4 and 5 showed almost complete regeneration of spermatogenic cells with increase in mean diameter of tubules, significantly in- creases in AR and decreases in caspase-3 expression. Conclusion: D.M produce damage in the testicular tissue and the concomitant administration of vit-E with metformin was shown better effect than metformin alone.