It is stated in studies that irisin, which is defined as an important member of both myokine and adipokine family, is an exercise hormone. The irisin hormone is the proteolytic product of fibronectin type III domain 5 (FNDC5) protein, and it transforms white adipose tissues into brown adipose tissues through exercise, increases energy expenditure and causes heat production. It has been reported that it may have protective effects on the central nervous system and may paly roles in the prevention of many metabolic diseases such as obesity and type 2 diabetes, in many systemic diseases including malignant tumors. Although it is stated that irisin is an exercise hormone, it is stated that irisin causes conflicting results in different studies on different subjects, at different time periods, by applying different exercise types. For this reason, studies continue today in order to fully elucidate both the mechanism of action between irisin and exercise and the role of irisin on metabolic diseases and the central nervous system. In this review, information about the irisin hormone, which is claimed to be associated with energy metabolism and exercise, is given and the studies are summarized.