We encountered a 74-year-old woman with a chief complaint of progressive right-sided back pain for more than 1 month. Physical examination and laboratory tests revealed no abnormalities. Multislice computed tomography (MSCT) showed dilatation of the inferior vena cava (IVC). An intraluminal mass of about 8.1 × 5.5 × 3.6 cm in size was found in the IVC, with big central necrosis and irregular peripheral enhancement. The tumor arose from the IVC just beneath the renal vein and reached the iliac bifurcation. Cavography demonstrated a filling defect with complete occlusion of the IVC and extensive collateral circulation. The patient underwent complete resection of tumor and vascular prosthetic graft. Pathological diagnosis was leiomyosarcoma. Because of its low incidences and atypical appearance, we highlight the significance of the imaging feature in its diagnosis in this article.