We present a rare case of congenital thoracic aortic aneurysm (TAA) complicated with dissection in a nine-year-old girl with Noonan syndrome and atrial septal defect. She presented with rapid breathing and upper respiratory tract symptoms. Chest X-ray revealed a huge upper mediastinum with cardiomegaly. Echocardiogram showed possible ascending TAA. Computerized tomography angiogram of the aorta revealed huge aortic root-ascending TAA with small aortic dissection. Despite immediate treatment, the patient passed away due to severe airway compromise.