Background: The concurrent global epidemics of type-2 DM and vitamin D deficiency raise the question whether vitamin D deficiency should be included among the risk factors for DM. Evidence is accumulating on the possible role of vitamin D in the pathogenesis of type 2 diabetes. Objectives: assessing 25-hydroxy vit D level in type-2 diabetes mellitus and correlating it with insulin resistance and other parameters. Patients and Methods: This study had been carried out in the diabetes clinic of Internal Medicine Department and laboratory part was done in Clinical Pathology department, Faculty of Medicine, Al-Azhar University during the period from January 2015 to October 2017.      This study included a total number of 60 adult subjects (above 18 years old), the subjects were divided into 2 groups: Group (A): Forty diabetic patients (type 2 diabetes mellitus) and Group (B): twenty non diabetic persons. Results: 25(OH)D level was lower in diabetic patients than in non-diabetic group with a significant difference. Conclusion: 25(OH)D was low in diabetic patients denoting that vitamin D status has a role in maintaining glucose homeostasis.