Evidence suggests that opioids can modulate gonadal function, with consequent decreased release of sex hormones. We attempted to investigate the sexual function of males using tramadol hydrochloride (HCL) and its relationship to levels of free testosterone, luteinizing hormone, and follicle stimulating hormone, and to compare them with heroin use disorder patients and healthy controls. Our sample consisted of 60 opiate use disorder patients (assessed by Structured Clinical Interview for DSM-IV Axis I) (30 heroin and 30 tramadol) and 30 healthy controls. Sexual dysfunction was assessed using the International Index of Erectile Function. Free testosterone, follicle stimulating hormone, and luteinizing hormone levels were measured in morning blood samples using enzyme-linked immunosorbent assay (ELISA). Results showed that there was a decrease of luteinizing hormone and free testosterone levels in opiate use disorder patients compared with healthy controls, with heroin-dependent patients having significantly lower levels than those using tramadol. Opiates’ effect on follicle stimulating hormone had mixed results. Opioid-dependent patients (both tramadol HCL and heroin using patients) developed sexual dysfunction more than healthy controls, which was generalized, with erectile dysfunction being the most affected domain. These findings are of ultimate importance, considering the fact that people use opioids to enhance their sexual performance in many countries.