Background: Diabetic nephropathy is one of the most common microvascular complications of type II diabetes mellitus that may lead to renal failure. Vitamin D is a fat-soluble vitamin and its deficiency is associated with an increased risk for cardiovascular and diabetic nephropathy. There were controversial studies about the role of vitamin D in diabetic nephropathy. This work aimed to study the protective and therapeutic roles of vitamin D against hypertension accompanied by diabetic nephropathy in type II diabetes mellitus and to find out a possible mechanism of its effect. Methods: A total of 36 male local strain albino rats. They were randomly divided into Group I: the control group and Group II: The experimentally induced type II diabetic group which was subdivided equally into Group 1(diabetic nephropathy group), Group 2(vitamin D prophylactic group), Group 3(metformin prophylactic group), Group 4(metformin and vitamin D prophylactic group) and Group 5( treated diabetic nephropathy). Fasting serum insulin, glucose, lipid profile, angiotensin II and kidney function tests were estimated. BMI, GFR, and HOMAIR were calculated in all groups at the end of the experiment. Also, arterial blood pressure was measured. Results: Vitamin D and metformin alone and in combination or treated diabetic nephropathy group induced a significant increase in SOD, urinary creatinine, and HDL with a significant decrease in serum insulin, glucose, triglycerides, cholesterol, LDL, creatinine, urea, proteinuria, angiotensin II, MDA and ABP. This effect was significant in the vitamin D/metformin combination group compared to the use of either vitamin D or metformin alone. Conclusions: Vitamin D may have a protective and therapeutic role in hypertension and nephropathy in type II diabetes mellitus. Keywords: Vitamin D; diabetic nephropathy; hypertension.