A 44-year-old woman presented with an acute inferior ST elevation myocardial infarction, followed by a stroke in the right hemisphere. To search for a cardiac source of embolism, a transesophageal echocardiogram was performed, which showed a mass obstructing the origin of the right coronary artery. The mass was surgically excised and a histologic examination confirmed its thrombotic origin. The diagnosis of antiphospholipid antibody syndrome was confirmed by positive lupus anticoagulant antibodies.