Background: Evaluation of sexual disorders among persons receiving methadone replacement therapy is of great importance, because these problems may lead to non-compliance and relapse. This study aimed to estimate the effect of methadone maintenance therapy (MMT) on sexual function among addicted Iranian men using met-analysis.Methods: Investigating the available data banks, relevant studies were identified. After exclusion of duplicates, irrelevant papers and low quality articles, eligible papers were entered into the meta-analysis. Prevalence and standardized mean difference of sexual function scores were illustrated by forest plots based on sexual desire, orgasm and erectile function.Findings: During the primary search, 5341 evidences were identified. After application of the inclusion/exclusion criteria and quality assessment, nine papers were detected eligible for final meta-analysis. Total prevalence [95% confidence intervals (CI)] of sexual disorders and erectile dysfunction among Iranian men under methadone therapy were estimated as 66.3% (27.1-105.5) and 77.5% (61.9-93.1), respectively. The standardized mean differences (95% CI) of Sexual desire, orgasm and erection before and after methadone therapy were estimated as 0.16 (-0.68, 0.99), -0.01 (-0.75, 0.74) and 0.11 (-0.41, 0.64), respectively.Conclusion: This meta-analysis showed that methadone therapy did not significantly influence the sexual desire, erectile function and orgasm among opium dependent men.