The inferior vena cava (IVC) may develop abnormally because of its complex embryogenesis. An understanding of congenital variants such as duplication of the IVC is essential for clinical interventions, particularly those performed by surgeons and radiologists. We herein describe five patients who were diagnosed with duplication of the IVC by computed tomography or angiography and summarize their imaging and clinical features. All five patients were men aged 46 to 78 years. Two of the patients had pulmonary embolism and deep vein thrombosis and were treated by placement of an IVC filter and catheter-directed thrombolysis. The IVC in all patients ascended on either side of the abdominal aorta. All left IVCs terminated in the left renal vein, which crossed the aorta and joined the right IVC. The average follow-up time was 29 months (range, 14-46 months), and no patients developed venous thromboembolism or recurrence of thrombosis. Duplication of the IVC can be diagnosed by computed tomography and angiography. Its course and relationship with the renal vein must be identified for accurate planning of IVC filter placement in the setting of deep vein thrombosis and pulmonary embolism.