Subclavian steal syndrome (SSS) is caused by hypoplasia of a vertebral artery or stenosis or occlusion of the subclavian artery or the brachiocephalic artery with subsequent retrograde filling of the subclavian artery via the contralateral vertebral artery. Symptoms of SSS are due to vertbrobasilar insufficiency or ischemia of the ipsilateral upper extremity, and they may include dizziness, syncope, ataxia, arm claudication, hand numbness or a decrease in brachial blood pressure on the affected side. However, most SSS cases are asymptomatic and they are classified as subclavian steal phenomenon (SSP). Atherosclerosis is the common cause of SSS, and Takayasu arteritis, neurofibromatosis, trauma, embolization, congenital vascular anomalies and surgical interruption of the subclavian artery can be identified among the other causes. We describe a rare case of hypervascular thyroid nodule presenting with features of SSP. The patient was hospitalized with acute cerebral infarction due to middle cerebral artery (MCA) severe stenosis. The patient had conservative therapy in the acute stage, and underwent STA-MCA anastomosis for MCA stenosis in the chronic stage. SSS was asymptomatic although there was laterality in blood pressure in the patient's bilateral upper limbs. Thyroid tumor was regarded as benign by radiological findings, laboratory data, and physical examination. If SSS becomes symptomatic, removal of the thyroid tumor may be indicated.