Pulmonary blastoma is rare and its prognosis very poor. A 6-year-old boy was referred to our hospital with chest pain. Computed tomography demonstrated that the left pleural cavity was filled with a tumor. Cardiac echocardiography demonstrated that the tumor had invaded through the pulmonary vein into the left atrium and that the tumor extended into the left ventricle. Part of the tumor was adhered to the anterior leaflet of the mitral valve. To increase operative radicality, an autotransplantation technique was performed concomitantly with resection of the original lesion. Through a median sternotomy, a moderate hypothermic cardiopulmonary bypass was established to obtain cardiac arrest. First, longitudinal incision of right-sided of the left atrium was made. The tumor invaded into the left atrium through the left superior pulmonary orifice. The ascending aorta, the main pulmonary artery, and both caval veins were transected. The left atrium was incised along the pulmonary venous orifices. The heart was completely removed from the mediastinum and transferred to another table. Resection of the intracardiac metastatic lesion and mitral valve replacement was accomplished. During this time, thoracic surgeons performed a left pneunectomy. The left atrial wall around the left pulmonary venous orifices was resected in combination with the left lung. After the deficit of the left atrial wall was repaired with a Gore-Tex patch, the heart was replaced and we reconstructed the great arteries and caval veins. The autotransplantation technique is a useful procedure for combined lesions of the heart and lung.