The objective of this paper is to review the evidence testing the possible benefit of vitamin D replacement on diabetes control and complications. Type 2 diabetes mellitus (DM 2) has become a significant global health care problem and its reported incidence is increasing at an alarming rate. Despite the improvement in therapy and development of new drugs, treatment is still not optimal especially with the associated adverse effects of most of the available drugs. New efforts are shifted toward disease prevention and a search for safer drugs. New mounting evidence is associating low vitamin D to diabetes mellitus and as such many studies were conducted to test the effect of vitamin D replacement on incidence of diabetes, diabetes control as well as diabetes complications. Although these studies present several limitations, vitamin D replacement seems to have beneficial effect on all aspects of diabetes: incidence, control and complications. Further longer term and more powered controlled trials are necessary to draw firmer conclusions on this beneficial role of vitamin D treatment on DM.