It is estimated that over 1 billion people worldwide have a deficiency of vitamin D, also known as hypovitaminosis D, which the World Health Organization has defined as a public health problem. Beyond its historical homeostasis regulatory function of calcium and phosphorus, in relation to the preservation of the skeletal system, several studies show today a close connection between hypovitaminosis D and the genesis of rheumatic, autoimmune, neoplastic, and cardiovascular diseases. With exclusive reference to cardiovascular aspects, multiple heart diseases such as hypertension, myocardial ischemia, and heart failures might have deficiency in vitamin D as an important causative factor. Because of the influence of concomitant pathologies caused by antibiotic-resistant agents, the function of this vitamin should be critically evaluated. However, the role of vitamin D remains to be established; only a few studies have tested the effects of its supplementation in patients with chronic heart failure diseases, and reported results are unclear. It is important to implement studies in this field in order to assess the real benefits induced by vitamin D supplementation in cardiovascular patients and, in particular, in patients with heart failure. Should the research confirm actual clinical improvement after treatment with vitamin D, such a supplementation might represent a new low-cost therapeutic approach to improving quality of life.