Introduction: Paraovarian cysts develop inside the broad ligament and some may reach a large size with possible complications. Case: An 18-year-old woman presented with a two-month period of rapid abdominal distension, dyspnea, and dysuria. Examination revealed a large fluid filled mass reaching the xiphi-sternum. CT scan revealed an adnexal cyst measuring 22×21×9.5 cm compressing the urinary bladder and approaching the diaphragm. Surgery was done through a mid-line incision, delivering part of the cyst and closed evacuation of some of the fluid to decrease its size before complete exteriorization for fear of spillage of a possible malignancy followed by its excision. No ascites or palpable lymph nodes were detected. Histopathology result showed papillary serous cystic tumor with onecm focal border-line changes. No recurrence was detected after one year follow-up. Conclusion: Open surgery is the best option to treat large cysts. Closed system aspiration of the cyst is safe and effective before its excision.