Aim: The aim of this study is to report a case of papillary thyroid carcinoma (PTC) with direct intravascular extension into the left internal jugular vein, resulting in tumor thrombus into the left innominate vein. Background: PTC is the most common of the four histological subtypes of thyroid malignancies,1 but PTC with vascular invasion into major blood vessels is rare.2 The incidence of PTC tumor thrombi was found to be 0.116% in one study investigating 7,754 thyroid surgical patients, and, of these patients with tumor thrombus, none extended more distal than the internal jugular vein.3 Koike et al.4 described a case of PTC invasion into the left innominate vein that was managed by a two-stage operative approach. Case description: A 58-year-old male presented with a rapidly growing left thyroid mass. Fine needle aspiration cytology (FNAC) suggested PTC and surgical exploration confirmed tumor extension into the left internal jugular vein. Continued dissection revealed a large palpable intraluminal tumor thrombus extending below the clavicle into the mediastinum, necessitating median sternotomy. Conclusion: Aggressive one-stage surgical resection resulted in successful en bloc extirpation of the tumor, with negative margins. Follow-up at 22 months postoperatively demonstrated no evidence of recurrence. Clinical significance: This is the first case of PTC extension into the left innominate vein managed with one-stage surgical intervention with curative intent.