Introduction: Adipokines, compounds secreted from adipose tissue, are involved in metabolism control. Omentin is one of the adipokines with different biological roles. Serum levels of Omentin were found to be associated with BMI, insulin resistance, metabolic syndrome, diabetes, and cardiovascular disease in several studies. The aim of this study was to assess the association between omentin level and the PolyCystic Ovarian Syndrome. Materials and Methods: This case-control study was performed on 45 patients with Poly Cystic Ovarian Syndrome and 45 normal individuals as controls. BMI and fasting omentin and insulin serum levels were measured by Enzyme-Linked Immunosorbent Assay (ELIZA) method, fasting glucose serum level was measured by enzyme-calorimetric method and insulin resistance index (HOMA-IR) was measured using the relevant equation. Data was analyzed using the independent t-test, Pearson correlation coefficient and by SPSS 16 software. Results: Omentin serum levels in the patient PCOS group were significantly lower in patients with polycystic ovarian syndrome than in controls. Insulin and glucose serum levels in the PCOS group were significantly higher than in controls, indicating these patients had insulin resistance. There was no significant correlation between serum levels of omentin and HOMA-IR between cases and controls. Conclusion: This study shows that serum omentin level decreased in PCOS patient in comparison with BMI-matched controls. The findings of this study suggest that changes in omentin serum level may be considered as a criterion of PCOS.