Blood flow obstruction through superior vena cava leads to superior vena cava syndrome (VCSS). The most common cause of the VCSS is malignancies. Enlargement goitre is an unusual cause of VSSS. A patient with superior vena cava syndrome secondary to enlarged thyroid gland was presented in this case report. An 84-year-old man presented to endocrinology unit with gradually increasing neck mass, dysphagia, and shortness of breath. His physical examination revealed webbed neck with a marked thyroid swelling and multiple dilated tortuous veins with enlarged venous collaterals. An anterior posterior chest radiograph showed a widened superior mediastinum. The ultrasonography showed retrosternal goitre with heterogeneous parenchyma and nodules with cystic-necrotic degeneration. Neck computed tomography revealed heterogeneous, hypertrophic, nodular thyroid gland with multiple calcification and mediastinal extension with narrowed trachea. Thyroid function test was within normal limit. Enlargement goitres are easily recognised however, the initial presentation of superior vena cava syndrome due to substernal goitres with mediastinal extension is unusual.