Superior vena cava (SVC) syndrome mostly presents the typical and unmistakable symptoms and signs, such as edema and venous distension of the face, neck, arms, and upper chest wall. Dyspnea and symptoms of airway obstruction are often the complaints of conscious patients. However, SVC syndrome if develops intraoperatively may become indistinguishable in view of the lack of utterable complaints of the patient and variable degrees of clinical presentation. We present a male patient who sustained an iatrogenic subclinical SVC syndrome in the course pneumonectomy. Airway obstruction was initially noted during the replacement of the double lumen endobronchial tube (DLT) by an ordinary endotracheal tube at the end of operation, which threw the patient into an acute precarious condition. Although he was conservatively treated with thrombolytic agent and anticoagulant, the patient eventually expired due to pulmonary embolism. The possible reasons for delayed diagnosis, intraoperative management, and prognosis of this case are discussed.