The patient was a 65-year-old female with metastasis of thyroid papillary carcinoma at the right upper mediastinum. The tumor, which invaded almost the entire length of the right brachiocephalic vein, was resected via a modified trap-door thoracotomy. The modification was the additional resection of the first rib from inside the thorax, which provided a sufficient exposure from the distal side of the brachiocephalic and subclavian vein. Because the subclavian and internal jugular veins could be clamped under this thoracotomy, the entire right brachiocephalic vein could be reconstructed by graft without excessive difficulty. Modified trap-door thoracotomy is a useful approach in the resection of malignancies which invade the brachiocephalic and subclavian vein.