According to the World Health Organization (WHO), the definition of infertility is ‘the inability of a sexually active, non-contracepting couple to achieve spontaneous pregnancy in one year. The category ‘unexplained male infertility' (UMI) is reserved for infertile men with infertility of unknown origin with normal semen and in which female infertility factors have been ruled out. Some cases of unexplained male infertility could be due to IR, leading to hypogonadism and other metabolic features. To evaluate serum level of irisin in patients with idiopathic infertility. Serum irisin concentrations were measured in 30 male patients with idiopathic infertility, between the ages of 25 and 50 years and 20 healthy controls using enzyme-linked immunosorbent assay (ELISA). Serum levels of irisin in male patients with idiopathic infertility were found to be lower than in healthy controls (p=0.001). Decreased serum irisin probably reflect the role of irisin in the diagnosis of idiopathic infertility.