There is an increased risk of cardiovascular disease in women with premature ovarian insufficiency (POI). A relationship between cardiovascular disease and endocan levels has been shown. Endocan is a marker that is prominent in many diseases caused by endothelial dysfunction and can be measured in the blood. POI is also associated with endothelial dysfunction. The causes of POI include chromosomal and genetic defects, autoimmune processes, chemotherapy, radiation, infections and surgery, but many are unidentified (idiopathic). This study aimed to evaluate serum endocan levels in women with idiopathic POI. The blood for analysis was obtained at the early follicular phase of the menstrual cycle and endocan levels were measured using a commercially available enzyme-linked immunosorbent assay kit. There were 38 patients with idiopathic POI in the study group and 39 healthy subjects in the control group. The median ages of the women were not significantly different between the groups 34  years vs. 34  years, respectively (p = .862). The median endocan level was not different in the POI and control group 769  vs. 1077  pg/mL, respectively (p = .603). Endocan is not associated with the cardiovascular diseases risk linked with endothelial dysfunction in idiopathic POI.What is already known on this subject?There is an increased risk of cardiovascular disease in premature ovarian insufficiency (POI) due to the decreased level of oestrogen, which is linked with endothelial dysfunction. What do the results of this study add?This study showed that endocan is not associated with the cardiovascular disease risk linked with endothelial dysfunction in idiopathic POI. What are the implications of these findings for clinical practice and/or further research?A marker to be used to predict the risk of cardiovascular disease in patients with POI could facilitate in improving the quality of life of these patients. Moreover, advantageous and easy-to-measure markers are needed in larger sample studies to better understand the cardiovascular diseases risk in POI.