Background: Polycystic ovary syndrome (PCOS) is a most prevalent endocrine diseases for females of childbearing age, and lead to an ovulatory infertility. It was shown that myonectin may be positively associated with insulin resistance parameters. Objectives: To evaluate serum myonectin levels and to determine the effects of metformin treatment on myonectin levels in patients with polycystic ovary syndrome. Patients and Methods: The Cross-Sectional Study carried out in the Department of Obstetrics and Gynecology Salahdeen general hospital in Tikrit city from 1st November 2022-30th January 2023. Patients diagnosed with PCOs depending based on the Rotterdam criteria. Participants were enrolled after all eligibility criteria were confirmed and informed consent completed. Sixty PCOS patients were selected as the PCOS group, while 30 healthy women matched for age with the PCOS patients were selected as the control group. Only 30 patients of them complete the follow up study and they agree to continue on metformin treatment during three months, the duration of the follow up. They take metformin 850 mg twice daily for three months and provide fasting blood samples on the second day of menstruation before and after treatment. The data collection done through: a designed closed and open-ended questionnaire, by using direct interviewing and Ultrasound examination, Laboratory examination. Myonectin, Luteinizing hormone (LH), Follicular Stimulating Hormone (FSH), and insulin were analysed by enzyme-linked immunosorbent assay (ELIZA) technique from Biomeriuex. Data were analyzed using SPSS for Windows 7. Results: The level of myonectin decreased significantly in PCOS patients compare to control group. The level of blood glucose, Insulin, and HOMA-IR, were increased significantly compared to the control. Serum LH levels were significantly higher, while the level of FSH were lowerin in women with PCOS than in controls. After metformin intake, all patients showed significant in decrease in gremlin concentration at p-values 0.05, but no significant difference (P>0.05) in myonectin level when compared to pre-treatment. Treatment resulted a significant decrease in in body mass index, Blood glucose, Insulin, HOMA-IR, testosterone and LH at p-values 0.05. However, the study found no significant difference (p > 0.05) in myonectin level between both groups in treated group with metformin compared with pre-treatment. Conclusion: Metformin testosterone and insulin resistance but can’t induce changes of myonectin level in patients with polycystic ovary syndrome.