Ectopic pregnancy accounts for approximately 2% of all pregnancies and is the most common cause of pregnancy-related mortality in the first trimester. Initial evaluation consists of β-hCG and pelvic ultrasonography. The fallopian tube is the most common location for an ectopic pregnancy. Other types of ectopic pregnancy include cornual, ovarian, cervical, scar, and abdominal pregnancy. In very rare cases, the abdominal pregnancy may be retroperitoneal. The diagnosis is seldom established before surgery and therapy is surgical resection of the ectopic mass. A 26-year-old woman visited our emergency department with sudden massive vaginal bleeding. She had undergone curettage 3 weeks before. But the transvaginal sonogram of the cul-de-sac revealed no fluid collection. She failed variable-dose methotrexate therapy. On laparoscopic operation, we found a cystic, conception-like structure in the retroperitoneum. Histology of resected structure showed chorionic villi. We describe this case with a brief review of the literature.