Differentiated thyroid carcinoma rarely shows gross angioinvasion with intraluminal tumor thrombus. Although there was no definite result of long-term survival, a vascular invasion or thrombus indicates poor prognosis. Total thyroidectomy with en block resection of involved vessels is known as the best surgical approach, and followed by postoperative radioiodine therapy. However, the effect of adjuvant external irradiation therapy remains in debate. We report a case of differentiated thyroid carcinoma with internal jugular vein tumor thrombus treated successfully by a complete surgical resection and postoperative radioiodine therapy.