Retroperitoneal ectopic pregnancy is an extremely rare type of ectopic pregnancy and is difficult to diagnose and treat. Due to its occult onset, it is life-threatening and often associated with high mortality. A 28-year-old woman was admitted to the Emergency Department of our hospital due to soreness of the left lower quadrant of the abdomen and amenorrhea for sixty days. Dilatation and curettage were performed at a local hospital to induce abortion but no gestational sac was found. Elevated plasma human chorionic gonadotropin (HCG) levels suggested ectopic pregnancy. An ultrasound showed an approximately 4.0 × 3.0 cm mass in front of the middle and upper pole of the left kidney. The plasma β-hCG level was 99286.00 mIU/mL. Under laparoscopy, an ovoid mass measuring about 4.0 × 5.0 cm below the left renal vessels and the abdominal aorta was successfully resected. Methotrexate (MTX; 50 mg/m2) was locally injected and the retroperitoneum was sutured. Villi were observed in histopathological sections. This case report highlights the importance of considering retroperitoneal ectopic pregnancy for patients with abdominal pain. Laparoscopic surgery by an experienced surgeon is the preferred method of treatment of this condition. Copyright © 2021. Published by Elsevier Inc.