Thromboses of the upper extremity and neck are rare and not as commonly seen as lower extremity deep vein thrombosis (DVT). Internal jugular vein thrombosis (IJVT) is a serious condition with a potentially fatal outcome. Jugular vein thrombosis refers to the formation of intraluminal thrombi anywhere from the intracranial part of the jugular vein to the junction between the internal jugular vein (IJV) and subclavian vein. The relationship between malignancy and thromboembolic disorders has been well established, as Trousseau first described it in 1865. Tumor cells are known to promote hypercoagulability by expressing tissue factors that activate clotting cascades and procoagulants while promoting interactions between the tumor cells, platelets, and endothelial cells via different cytokines, tumor antigens, and their immune complexes. We are reporting our encounter with a patient who presented with extensive left internal jugular vein thrombosis as the first presenting sign of primary lung malignancy.