We present a 30-year-old man with an acute middle cerebral artery territory infarction. A transesophageal echocardiogram showed a large, highly mobile mass attached to the patient's aortic valve. We discuss the differential diagnosis of a cardiac mass that includes infection, tumor, and thrombus. A complete workup showed no evidence of systemic infection but did reveal the presence of antiphospholipid antibodies. The patient also had a history of a right lower extremity deep venous thrombosis. Anticoagulation therapy was started, and follow-up showed complete resolution of the aortic valve lesion. This case highlights that when a valvular vegetation is encountered in a clinical setting that does not suggest infectious endocarditis, the diagnosis of antiphospholipid antibody syndrome should be considered. This case and our review of the literature suggest that vegetations in antiphospholipid antibody syndrome, no matter how large and ominous in appearance, can be treated successfully with anticoagulation and vigilant observation.