Vitamin D deficiency is a highly prevalent condition present in 30-50% Of the general population.A growing body of evidence points out to the fact that low 25 hydroxy vitamin D level has an adverse effect on cardiovascular disease and development of diabetes mellitus.The basis for these observations is linked to the fact that vitamin D has been shown to modulate immune and inflammatory reactions so that its deficiency causes a hyper-inflammatory state.Moreover hypovitaminosis D up regulates the renin-angiotensin-aldosterone system, and increases serum PTH levels, all of which contribute to increased incidence of hypertension, vascular and myocardial calcification, atherosclerosis, left ventricular hypertrophy and myocardial infarction, and in parallel decrease insulins secretion from pancreatic β cells while decreasing insulins sensitivity.The common pathophysiologic link between vitamin Ds deficiency, cardiac and diabetic disease will be discussed in detail as well as the available epidemiologic data and the clinical implications analyzed.