Severe acute respiratory syndrome coronavirus 2 infection can result in multisystem inflammatory syndrome in children (MIS-C). MIS-C can lead to myocardial dysfunction, heart failure, and multiorgan failure; the primary finding is hyperinflammation. Endothelial dysfunction has not been evaluated in patients with MIS-C. We investigated endothelial dysfunction and arterial stiffness parameters in patients with MIS-C. The study included 38 pediatric patients (20 males and 18 females aged 4-17 years, mean age 8.89 years) with MIS-C. Thirty-eight age-and sex-matched healthy individuals were enrolled as the control group. Systolic and diastolic ventricular measurements and systolic and diastolic measurements of ascending aorta diameter were performed by M-mode echocardiography. Endothelial dysfunction was evaluated using flow-mediated dilation by measuring the brachial artery diameter with a high-resolution probe. The MIS-C group had lower flow-mediated dilation than did the controls. The MIS-C group had decreased aortic strain and aortic distensibility values and correlations between decreased flowmediated dilation and reduced aortic strain, aortic distensibility, and reduced ejection fraction. Conclusion:The results show that patients with MIS-C had endothelial dysfunction and arterial stiffness. Furthermore, the degree of endothelial dysfunction correlated with reduced ejection fractions. What is Known:•Endothelial dysfunction and arterial stiffness are unknown in patients with MIS-C.•The effect of endothelial dysfunction and arterial stiffness on decreased cardiac function is unknown. What is New: •MIS-C patients have endothelial dysfunction and arterial stiffness.•There is a link between left ventricular dysfunction and reduced endothelial dysfunction in patients with MIS-C.