Objective Polycystic ovary syndrome (PCOS) is a common endocrinological disease in women of reproductive age and has a wide range of metabolic effects. Chronic low-grade inflammation and endothelial dysfunction plays a key role in the pathogenesis of PCOS and they are associated with an increased risk of cardiovascular disease. Endocan, is an inflammatory marker showing endothelial dysfunction. The aim of our study, to compare serum endocan levels in PCOS and healthy control groups and to determine the relationship between some cardiovascular risk factors and serum endocan levels. Materials and Methods This case-control study included 52 PCOS patients and 59 age-matched healthy controls. Patients were diagnosed as PCOS based on 2003 Rotterdam criteria. Demographic data, history of menstrual irregularity and infertility, polycystic ovary appearance in ultrasonography and hirsutism status were recorded. Endocan levels of PCOS patients and controls were compared. Data analysis was performed by using SPSS-22 for Windows (Statistical Package for Social Science, SPSS Inc. Chicago IL, USA®Z). Results The median (IQR) value of serum endocan level was 420.7 ng/L (355.2-570.3) in the PCOS group and 320.0 ng/L (219.9-455.9) in the control group (p=0.003). While there was no significant correlation between serum endocan and some cardiovascular risk factors such as waist circumference, hip circumference, BMI, LDL, triglyceride, systolic and diastolic arterial tension but a positive correlation was found between homeostatic model assessment insulin resistance (HOMA-IR) (r= 0.276, p= 0.003). Conclusion Serum endocan levels are higher in PCOS patients, in line with the literature. Endocan level shows a significant correlation with insulin resistance, one of the metabolic parameters. This may be a sign of early endothelial dysfunction in PCOS. Keywords endocan; endothelial dysfunction; polycystic ovary syndrome; inflammation Öz Amaç Polikistik over sendromu (PKOS), üreme çağındaki kadınlarda sık görülen endokrinolojik hastalıktır. PKOS'ta izlenen kronik düşük dereceli inflamasyon ve endotel disfonksiyon artmış kardiyovasküler hastalık riski ile ilişkilidir. Endocan, endotel disfonksiyonunu gösteren inflamatuar bir belirteçtir. Çalışmamızda PKOS ve sağlıklı kontrol grubunu serum endocan düzeyleri açısından karşılaştırmayı ve kardiyovasküler risk faktörleri ile serum endocan düzeyleri arasındaki ilişkiyi belirlemeyi amaçladık.