A rare case of fusiform aneurysm of the superior vena cava (SVC) in a 65-year-old Japanese woman is presented herein. Aneurysm of the SVC was detected incidentally as widening of the upper mediastinum on chest radiography and was further defined using magnetic resonance imaging, venography and chest computed tomography. Based on previous reports, conservative management was planned with anticoagulation therapy as prophylaxis against thrombotic complications rather than surgical resection for aneurysm.