The impact of vitamin D on multiple biological processes is nowadays widely accepted. Vitamin D deficiency has been linked with many diseases, including cardiovascular and neurological diseases, as well as with immune system function and its role during infections. An influence of vitamin D on the reproductive functions of women and men has been also reported. Endometriosis is one of the conditions responsible for infertility in women, and the contribution of vitamin D on the development of the disease has been investigated. Yet, a direct link between predisposition to endometriosis or severity of the disease and vitamin D status has not been defined. Some studies report no changes in vitamin D levels in endometriosis patients, compared to healthy controls, while others show a significant increase or decrease in vitamin D concentration in women suffering from endometriosis. Therefore, further studies are needed to establish the relationship between endometriosis and vitamin D status, which may be useful in designing vitamin D supplementation schedules for endometriosis patients, or in monitoring women at risk of developing the disease.