We report 2 cases of congenital pericardial defect with ruptured acute type A aortic dissection. Case 1: An 83-year old man presented with sudden chest and back pain, and computed tomography (CT) showed acute aortic dissection with left pleural massive effusion. Because of his unstable haemodynamic condition with low blood pressure, an emergency operation was performed. We observed small amounts of bloody pericardial effusion, massive left-sided bloody pleural effusion and a partial left-sided pericardial defect of the pulmonary artery. The ascending aorta was replaced. The postoperative course was uneventful. Case 2: A 79-year old man presented with fainting followed by cardiac arrest and was resuscitated. Chest CT showed acute aortic dissection and massive haemothorax. Emergency operation was attempted, but was given up. We observed partial left-sided pericardial defect of the pulmonary artery. Further, we reviewed 6 cases of congenital pericardial defect with ruptured acute aortic dissection, including our 2 cases. In all the cases, the patients did not develop cardiac tamponade but had massive haemothorax due to congenital pericardial defects leading to confusion in diagnoses and surgical strategies. Therefore, it may be necessary to consider congenital pericardial defects before performing an operation in case of acute type A aortic dissection with massive haemothorax.