A 68-year-old woman presented for reevaluation of progressively worsening dyspnea over 2 years. Imaging 4 months prior included unremarkable chest CT, pulmonary function tests, and pulmonary angiogram. On reevaluation, transesophageal echocardiogram was performed; a large right atrial mass was discovered. Magnetic resonance imaging and chest CT defined the extent of the mass. Fluoroscopically guided biopsy of the mass confirmed leiomyosarcoma. Immunostains were positive for smooth muscle actin and desmin. Combined PET/CT scan was done for staging. The leiomyosarcoma, noted to originate from the inferior vena cava intraoperatively, was resected in toto. Postoperative course was unremarkable and her dyspnea gradually improved.