Ectopic insulinoma is a very rare and dormant tumor.Here we report the case of a 79-year-old female who presented with repeated episodes of hypoglycemia and was diagnosed with insulinoma based on laboratory and imaging examinations.Computed tomography and positron emission tomography revealed a tumor in the retroperitoneum under and left of the hepatoduodenal ligament, which was resected successfully using a laparoscopic approach.Pathologic results revealed an ectopic insulinoma, which was confirmed immunohistochemically.Ectopic insulinomas are accompanied by hypoglycemia that can be misdiagnosed as drug- or disease-induced.These tumors are difficult to diagnose and locate, particularly in atypical cases or for very small tumors.Synthetic or targeted examinations, including low blood glucose, elevated insulin, proinsulin, and C-peptide levels, 48-h fasting tests, and relevant imaging methods should be considered for suspected cases of insulinoma.Surgery is the treatment of choice for patients with insulinoma, and laparoscopic resection is a feasible and effective method for select ectopic insulinoma cases. Ectopic insulinoma is a very rare and dormant tumor. Here we report the case of a 79-year-old female who presented with repeated episodes of hypoglycemia and was diagnosed with insulinoma based on laboratory and imaging examinations. Computed tomography and positron emission tomography revealed a tumor in the retroperitoneum under and left of the hepatoduodenal ligament, which was resected successfully using a laparoscopic approach. Pathologic results revealed an ectopic insulinoma, which was confirmed immunohistochemically. Actopic insulinomas are accompanied by hypoglycemia that can be misdiagnosed as drug- or disease-induced These tumors are difficult to diagnose and locate, particularly in atypical cases or for very small tumors. Synthetic or targeted examinations, including low blood glucose, elevated insulin, proinsulin, and C-peptide levels, 48-h fasting tests, and relevant imaging methods should be considered for reduced cases of insulinoma.Surgery is the treatment of choice for p atients with insulinoma, and laparoscopic resection is a feasible and effective method for select ectopic insulinoma cases.