Arterial thoracic outlet syndrome is a rare condition characterized by compression of the subclavian artery, often with post-stenotic aneurysm formation. Artery-to-artery embolic strokes related to thoracic outlet syndrome have been reported in the posterior circulation and in the ipsilateral anterior circulation. We present a case in which a thrombus secondary to thoracic outlet syndrome caused a contralateral anterior circulation stroke in an adolescent and postulate mechanisms of this rare occurrence. This case demonstrates that a subclavian thrombus due to thoracic outlet syndrome can take a circuitous path and cause an anterior circulation stroke contralateral to the diseased subclavian artery. In addition, this case illustrates the importance of a high index of suspicion for thoracic outlet syndrome in patients with stroke and associated arm pain or discoloration.