We describe surgical and adjuvant therapeutic management of a right ventricular (RV) sarcoma and pulmonary artery occlusion. Echocardiographic evaluation of a 39-year-old man with exertional dyspnea revealed a tumor mass in the right ventricle, pulmonary trunk, and bilateral pulmonary arteries. The tumor was resected with concomitant pulmonary valvotomy, but the resection was incomplete. The RV outflow was reconstructed with an allograft patch, and a stentless valve was implanted for pulmonary valvular function. The pulmonary trunk and arteries were enlarged with allograft patches. The tumor was undifferentiated sarcoma and caused postoperative pulmonary artery restenosis. Radiotherapy improved pulmonary perfusion (reduction of RV pressure), but the patient died of brain metastasis. Undifferentiated cardiac sarcomas associated with pulmonary hypoperfusion should be resected even if incompletely, and radiation therapy could alleviate reduced pulmonary perfusion.