Uterine leiomyosarcoma is a rare and aggressive malignant tumor arising from the smooth muscle cells of the myometrium, which rarely metastasizes to the heart. We report the case of a 49-year-old Chinese woman who underwent a successful one-stage surgical intervention after an initial diagnosis of intravenous uterine leiomyomatosis. However, her postoperative biopsy showed the presence of low-grade malignant uterine leiomyosarcoma with intravenous and right atrium extension. It is our conclusion that surgical resection is the mainstay treatment for this type of condition.