Background: We report a rare case of epithelioid uterine leiomyosarcoma presenting with tumor rupture, a rare complication of uterine sarcomas. Case: The patient was a 47-year-old woman who was receiving filgotinib for ulcerative colitis and presented with genital bleeding. A uterine mass was detected, and malignancy was suspected. During the workup, she developed fever, genital bleeding, and lower abdominal pain and re-visited the emergency department. Coronavirus disease and intrauterine infections were suspected, and she was hospitalized. Despite antibiotic administration, no clinical improvement was observed. Computed tomography revealed irregular margins between the tumor and uterine muscle layer on the uterine fundus, raising strong suspicion of malignant tumor rupture. She was transferred to a tertiary care center and underwent total hysterectomy. Intraoperatively, the rupture site was covered by the omentum, and intra-abdominal spread of inflammation was limited. Histopathological examination revealed coagulative necrosis, proliferation of tumor cells with round nuclei, and numerous mitotic figures, leading to a diagnosis of epithelioid uterine leiomyosarcoma. Local recurrence at the vaginal stump was observed 10 months postoperatively, and treatment is ongoing. Conclusions: In this case, the diagnosis was triggered by genital bleeding. During evaluation, tumor rupture occurred, but clinical symptoms were minimal due to coverage of the rupture site by the omentum, making diagnosis challenging. Thorough screening for malignancy and careful monitoring are essential when using Janus kinase inhibitors.