Introduction: Retroperitoneal liposarcoma is a malignant, primitive and rare mesenchymal tumor. We report an observation of a retroperitoneal liposarcoma mimicking an ovarian tumor. Case: A 36-year-old female presented a pelvic pain type gravity whose examination found an abdominopelvic mass, an abdominopelvic computed tomography showed a large abdominal-pelvic mass with a fatty component leading to the diagnosis of ovarian teratoma. At exploratory laparotomy, we found a large abdomino-pelvic mass of 30 × 35 cm, and a large resection was realised. The histopathologic examination found a liposarcoma well differentiated (grade 1). Conclusion: The different pathological aspects, the therapeutic options and the prognostic factors of the abdominal liposarcomas will be discussed in this article.