Floating masses in ascending aorta are an uncommon source of embolism. We report the case of a 46-year-old woman, smoker, on synthetic progestagen, with no previous history of thrombotic events, who was admitted to our emergency department for an acute anterior myocardial infarction. Coronary angiogram showed occlusion of left main coronary trunk. Recanalization of the artery was obtained. Ascending aorta angiogram revealed a free floating mass attached to the aortic wall without evidence of aortic dissection. Transesophageal echocardiography confirmed the presence of a pedunculated mobile mass attached to the aortic wall superior to the left coronary ostium. The patient underwent urgent surgery. Intraoperatively a floating thrombus was localized in the posterior wall of ascending aorta. At macroscopical examination aortic wall and leaflets were normal. Post-operative low cardiac output refractory to inotropic drugs and intraaortic balloon counterpulsation required a circulatory assist device. Consequences for the patient were catastrophic in terms of outcome.