Obesity and obesity-related diseases including insulin resistance and metabolic syndrome (MetS) pose a great risk for cardiovascular diseases development. Skeletal muscle as an endocrine organ has pivotal role on secreting physiological factors such as hormones and myokines. Irisin that is one of these miyokines also known as hormone is secreted mainly from muscle tissue in response to exercise. It is dependent to fibronectin type III-containing protein 5 (FNDC5) that is a membran protein and encoded by FNDC5 gene. After discovering of FNDC5 by Boström et al., irisin’ metabolic effects have been investigated so far. Irisin has mainly effects on muscle, adipose tissue, pancreas, liver, nervous system and bone. In studies conducted to date, obtained findings regarding the relationship of irisin status with obesity, insulin resistance and MetS are contradictory. Although it was determined that irisin concentration is higher in individuals with metabolic disorders before mentioned in some studies, is lower irisin concentration were observed in some other studies. Additionally, the irisin molecule has no a receptor yet discovered. Therefore it is thought that the discovery of irisin molecule receptors and the determining of the tissues where these receptors are present will be useful in understanding the mechanism of action of the irisin. In this review, we aimed to investigate potential health effects of irisin on obesity, insulin resistance and MetS additionally examine underlying mechanisms of the association between circulating irisin and metabolic disorders.