Vitamin D is a fat-soluble steroid hormone whose main role is calcium and phosphates homeostasis. However, lately Vitamin D receptors and Vitamin D metabolizing enzymes have been found in other tissues including male and female reproductive tissue. They have been located in granulosa cells, endometrium and promoter regions of genes involved in reproduction. In vivo studies on animals and In vitro studies on human cells have shown that Vitamin D has a role in folliculogenesis regulation, sex hormone and AMH secretion regulation, placentation, as well as immunomodulatory role in endometrium. Those information, as well as some studies showing up to 40% of reproductive age women are Vitamin D insufficient, that figure going up to 80% in women with polycystic ovary syndrome, have made scientists research possible benefits of Vitamin D in clinical practice, as an affordable and widely accessible therapy. The aim of those clinical trials was to establish whether Vitamin D can improve assisted reproduction technologies outcomes. Some of those clinical trials included all women going through assisted reproduction technology procedures, some only women with polycystic ovary syndrome and some only women with endometriosis. So far, researchers couldn't find any benefits of Vitamin D on assisted reproduction technology procedure outcomes in any of the researched groups of women. However, all the researchers remarked that current clinical trials are not sufficient to make a final conclusion regarding the role of Vitamin D in assisted reproduction technology in women. On the other side, Vitamin D receptors and metabolism enzymes have also been located in spermatozoa, Leydig and Sertoli cells. In vivo studies on animals and In vitro studies on human cells have shown that Vitamin D can increase sperm mobility, volume and count, as well as regulate testosterone secretion. But, the results of clinical trials are contradictory and a final conclusion on the role of Vitamin D in male fertility and assisted reproduction technology outcomes cannot be made without further research.