Aneurysms of the thoracic aorta rarely occur in children. We present a female neonate who was referred to our hospital due to a heart murmur associated with cough and fever at 22 days of age. Both the echocardiography and aortography displayed an aneurysm of the ascending aorta at the aortic root. A patent ductus arteriosus (PDA) flow was detected on admission but it was not detectable when she was 3 months old. Neither physical characteristics of Marfan nor Turner syndrome were found, but she has had a huge cutaneous hemangioma over the right trunk since birth. The aneurysm did not progress during one year of follow-up. The etiology might be idiopathic or medial agenesis. Surgery will be warranted only if the aneurysm enlarges.