We present a 58-year-old female patient who underwent resection of a leiomyosarcoma arising from the right ovarian vein. She was referred to our hospital because of lower abdominal pain that had been present for 1 month prior to the visit. Ultrasound examination revealed a well-defined, smooth, lobulated, highly vascular mass(57 mm)adjacent to the distal portion of the duodenum. Contrast-enhanced computed tomography revealed the contrast enhancement mass (60 mm)located surround the right ovarian vein. In abdominal magnetic resonance image examination, the mass exhibited isointense signal on T1-weighted images, high signal on T2-weighted images, and restricted diffusion on diffusion- weighted images. We suspected primary leiomyosarcoma of the ovarian vein and proceeded with surgical intervention. On intraoperative findings, the mass was in contact with the duodenum and the inferior vena cava but dissection was easily achieved. We excised the mass together with the right ovarian vein. Pathological findings showed the mass was composed of proliferating spindle-shaped cells arranged in bundles. Some areas showed polygonal nuclear atypia and abnormal mitotic figures. Additional immunostaining showed positive for α-SMA, caldesmon, calponin, and negative for desmin, CD34, CKA1/AE3, S100. Based on the intraoperative findings, we diagnosed it as leiomyosarcoma arising of the right ovarian vein.