Complex aortic atheromas are an important differential diagnosis to consider in evaluating sources of arterial embolization. Diagnosis of the embolic source is an essential first step, so treatment can then be initiated to prevent further reoccurrence. We report the case of a 36-year-old man, without significant medical history, who presented to the University of Illinois at Chicago with peripheral vascular embolism to the lower extremities. Computed tomography with contrast angiography and transthoracic echocardiography failed to reveal a source of the thromboembolism. A complex mobile atheroma was discovered in the ascending aorta during transesophageal echocardiography. The case presented is noteworthy when considering the following: the relative rarity of complex atheromas of the ascending aorta, the young age of the patient with no history of atherosclerotic disease, and the failure of computed tomography angiography to reveal the embolic source despite literature supporting high sensitivities for aortic plaque detection compared with transesophageal echocardiography.