Congenital partial pericardial defect is a rare anomaly that causes no symptoms and is often noticed by chance at autopsy or thoracotomy. During an operation on a patient with bronchiectasis, a partial pericardial defect and anomaly of left phrenic nerve were found incidently. A 58-year-old man complaining hemoptysis was referred to our hospital for surgical treatment of the left cystic bronchiectasis. During a thoracotomy, a partial pericardial defect was noticed. Moreover the left phrenic nerve could not be found within the operative field. We performed left pneumonectomy without repair of pericardial defect, and the patient had a satisfactory postoperative course. A relationship was suggested between congenital pericardial defect and the anomaly of the phrenic nerve.