Benign mediastinal cysts are challenging to diagnose. Although Endoscopic Ultrasound (EUS) and EUS-guided fine needle aspiration (FNA) can accurately diagnose mediastinal foregut cysts, little is known about their complications. This paper reports a rare case in which EUS-FNA performed on mediastinal hemangioma resulted in an aortic hematoma. A 29-year-old female patient was commissioned for EUS of an asymptomatic accidental mediastinal lesion. Chest CT revealed a 4.9×2.9×10.1 cm thin-walled cystic mass in the posterior mediastinum. EUS revealed a large, anechoic cystic lesion with a regular thin wall with negative Doppler. EUS-guided FNA was performed using a single-use 19-gauge aspiration needle (EZ Shot 3; Olympus, Tokyo, Japan), and approximately 70 cc of serous pinkish fluid was aspirated. The patient was in a stable condition with no signs of acute complication. One day after EUS-FNA, thoracoscopic resection for mediastinal mass was conducted. The purple and multi-loculated large cyst was removed. Upon removal, however, an aortic hematoma caused by a focal descending aortic wall injury was observed. After a few days of close observation, the patient was discharged upon stable 3D aorta angio CT findings. This paper reports a rare and severe complication of EUS-FNA, in which an aspiration needle caused a direct injury to the aorta. The injection must be performed carefully to avoid damaging the adjacent organs or digestive tract walls. (Korean J Gastroenterol 2023;81:168-172)