Follicular variant of papillary carcinoma thyroid is an aggressive variant of papillary carcinoma thyroid. It is more commonly associated with extrathyroidal extension and regional lymphadenopathy. It can rarely be associated with microscopic vascular invasion but tumor thrombus into great veins is a rare phenomenon. We present a case of 60-year-old male with follicular variant of papillary carcinoma thyroid with tumor thrombosis in superior thyroid vein and internal jugular vein (IJV). We report a case of a 60-year-old male who presented with a large swelling in the lower part of left side of neck for 4 months. Clinical examination revealed a hard swelling of 12x8 cm in left side of neck. Ultrasonography showed a solitary thyroid mass of the left lobe and a dilated left superior thyroid vein and ipsilateral IJV. Fine-needle aspiration cytology revealed follicular variant of PTC cells. Total thyroidectomy was done. A tumor thrombus was discovered in the superior thyroid vein and left IJV was found to be dilated. The left IJV with superior thyroid vein was ligated and excised. The patient recovered well after the operation with no local or distant metastasis detected. Follicular variant of PTC commonly spreads to the lymph nodes. Vascular spread via direct intravascular extension through superior thyroid vein is extremely rare. On palpation cord like IJV is felt on the involved side. Neck ultrasound play important role in the diagnosis. Aggressive surgical treatment with IJV ligation above and below the tumor thrombus is recommended to minimize the risk of potentially fatal complications of the intraluminal masses. Intravascular tumor extension into IJV of neck in follicular variant of PTC is rare and can be associated with serious consequences. Total thyroidectomy with thrombectomy with ligation of IJV must be done.