This study aimed to measure the serum endocan level of patients with erectile dysfunction (ED) and to investigate the possible association between the Endothelial-specific molecule-1 (Endocan) level and ED. Twenty healthy and sixty-four male patients included in the study were divided into four groups: severe ED (19 patients), moderate ED (24 patients), mild ED (21 patients) and control group (20 healthy men). The erectile function of all the patients was evaluated using the International Index of Erectile Function-5 (IIEF-5) questionnaire. The body mass index (BMI) of each participant was determined, together with levels of fasting blood glucose, total testosterone, low- and high-density lipoprotein cholesterol, triglyceride and endocan in serum samples. No significant difference was found between the three ED groups and the control group in terms of the mean age, BMI and the levels of cholesterol and fasting blood glucose (P>0.05). The mean serum endocan level was found to 1.076±0.5, 0.674±0.40 and 0.671±0.3 ng ml-1 in the severe, moderate and mild ED groups, respectively. This indicated that the highest value was obtained from the severe ED group, and the difference between the severe ED group and the other groups was statistically significant. In the control group, the serum endocan level was 0.73±0.46 ng ml-1, which was significantly higher compared to the moderate and mild ED groups (P<0.05). The significant difference between the control and ED groups in terms of the serum endocan level can assist in the evaluation of endothelial pathologies in the etiology ED.