We report a case of a large, B-cell lymphoma of the atria in a 65-year-old man who presented with obstructive right-heart failure, shortness of breath, cirrhosis, and ascites. A computed tomographic scan revealed a large cardiac tumor occupying both atria. The patient underwent debulking of the tumor and postoperative chemotherapy. Six months postoperatively he was alive and his symptoms of obstructive right-heart failure had improved; however, he had developed brain metastasis.