The systemic effects of COVID-19 disease are still largely uncertain and needs to be scrutinized with further trials. Endothelial dysfunction (ED) is responsible for the majority of adverse cardiovascular events. Flow-mediated dilation (FMD) is easily obtainable method to assess ED accurately. It is aimed to evaluate ED by measuring FMD following COVID-19 disease. Patients diagnosed with COVID-19 disease were recruited to the hospital two month after the discharge. Sex and age-matched healthy subjects were determined as the control group. Blood samples and FMD measurements were obtained from each participant. All subjects were divided into two groups according to the presence of ED determined by FMD measurements. These two groups were compared in terms of demographic features and the presence of recovered COVID-19 disease. A total of 92 subjects consisting of 59 without ED and 33 with ED were included in the study. ED (+) group was older (p = 0.015) and more likely to have hypertension (p = 0.044) and COVID-19 rate was higher in ED (+) group (p = 0.009). While neutrophil count (p = 0.047) and CRP (p = 0.036) were higher, eGFR (p = 0.044) was lower in ED (+) group. In the backward multivariable regression analysis, COVID-19 disease [OR = 3.611, 95% CI 1.069-12.198, p = 0.039] and BMI [OR = 1.122, 95% CI 1.023-1.231, p = 0.015] were independent predictors of ED. COVID-19 disease may cause ED which is the major underlying factor of cardiovascular diseases. Furthermore, COVID-19 disease may deteriorate the existing cardiovascular disease course. Detecting ED in the early phase or preventing by new treatment modalities may improve short and long-term outcome.