Hydatid disease is a parasitic infection that most commonly affects the liver and lungs, although the disease can arise in any part of the body. Cysts may mimic many benign and malignant conditions. The diagnosis cannot be confirmed preoperatively in all cases. A 44-yr-old menopausal woman was admitted to the department of gynecology with complaints of abdominal distention. A fixed abdominopelvic mass was identified. Radiology revealed a 20-cm mass with branched septations and solid components. CA-125 level was 55 kU/L, and Risk of Malignancy Index-2 score was 880. These findings suggested the presence of an ovarian neoplasm, and laparotomy was performed. Cystic masses measuring 22 cm and 4 cm, originating from the omentum majus and left ovary, respectively, were found during surgery. Frozen-section analysis revealed hydatid disease. Infracolic omentectomy and total abdominal hysterectomy with bilateral salpingo-oopherectomy were performed. Results of a serum Echinococcus hemagglutination test performed immediately after surgery were negative. The patient was prescribed albendazole for 6 mo and discharged on the third postoperative day with no complaints. The incidence of hydatid disease in the female reproductive system is very rare; however, clinicians must be aware of this disease and take necessary precautions while operating because any spillage may lead to anaphylactic shock and increased risk of recurrence.