True aneurysm of the inferior thyroid artery is extremely rare. A 52-year-old man complained of a pulsatile mass in the left side of the neck. A preoperative computed tomography (CT) showed an aneurysm (6.5 cm×4.5 cm) in the left side of the neck and 3 dimensional-CT revealed an inferior thyroid artery aneurysm. His postoperative course after an aneurysmectomy was uneventful. Pathological findings showed atherosclerotic changes. Inferior thyroid artery aneurysm should be considered in the differential diagnosis of pulsatile masses in the neck.