Floating thrombus in the ascending aorta is an uncommon source of embolism. We report a case of a 61-year-old man who was admitted to our hospital for transient brain ischemic attack. Transesophageal echocardiography showed a floating mass on the sinotubular junction. We started anticoagulation therapy immediately and performed surgical removal of the mass 5 days after the admission. Postoperative course was uneventful. He is now in good health and has no sign of recurrence. The etiology of this case is unclear, and the strategy is difficult to determine in terms of cerebral complications.