Endometrial stromal sarcoma (ESS) that arises from extrauterine endometriosis is a rare form of malignancy. We report the case of a 37-year-old ESS patient with extrauterine endometriosis who was treated with ifosfamide/cisplatin chemotherapy. A woman presented with epigastric pain and abdominal distension. Computed tomography imaging revealed a profuse amount of ascites, including a 12.4×12.3 cm sized posterior cul-de-sac mass composed of solid and cystic components. Cytoreductive surgery was performed to remove the mass and the histopathologic findings indicated ESS associated with extrauterine endometriosis. Six cycles of combination chemotherapy [ifosfamide (5 g/m) with mesna (1 g/m) and cisplatin (50 mg/m) (IP)] were administered. After a six-month of disease-free interval, recurrent ESS developed in the pelvic cavity and in both lung fields. Megace medication decreased tumor marker CA-125 for six weeks. However, the patient expired sixteen months after the cytoreductive surgery. ESS associated with extrauterine endometriosis showed response to IP chemotherapy and megace.