A 43-year-old man was admitted to our hospital complaining of dyspnea on exertion and dizziness. Transthoracic echocardiography revealed a mobile mass (3.5 x 1.0 cm) attached to the left atrial septum and transesophageal echocardiography showed the mass in the right atrium protruding through the patent foramen ovale into the left atrium. A mobile snake-like thrombus was apparent in the right atrium and right ventricle. The diagnosis was pulmonary embolism with impending paradoxical emboli.