Introduction. Leiomyosarcomas of vascular origin are particularly rare tumors occurring mainly in the inferior vena cava (IVC). They are malignant, slow-growing tumors with a poor prognosis. This paper reports on a rare case of surgical resection of an IVC leiomyosarcoma mimicking a hepatic tumor. Case Presentation. A 65-year-old Japanese male was admitted for evaluation of an abdominal tumor. Enhanced computed tomography of the abdomen revealed a slightly enhanced heterogeneous tumor, 18 mm in diameter, between the Spiegel lobe of the liver and the IVC in early-phase images, with no enhancement or washout in late-phase images. We diagnosed this tumor as either a hepatic tumor in the Spiegel lobe or a retroperitoneal tumor such as leiomyosarcoma or liposarcoma and performed a laparotomy. On the basis of surgical findings, we extirpated the tumor by performing a wedge resection of the wall of the IVC and suturing the primary IVC wall. Pathological findings led to a further diagnosis of the tumor as a leiomyosarcoma originating in the IVC. Thirty-seven months after the operation, multiple liver and lung metastases were detected, and the patient died from multiple organic failures. Conclusion. We experienced a rare case of a leiomyosarcoma of IVC mimicking hepatic tumor.