BACKGROUND Nesidioblastosis is a rare disease that is part of the differential diagnosis of pancreatogenic hyperinsulinemic hypoglycemia (PHH) in patients whose imaging studies do not localize insulinoma. Pancreatic heterotopia is a rare congenital abnormality characterized by pancreatic tissue anatomically separated from the main gland and found in 0.5% of abdominal surgeries. The purpose of this article is to provide a systematic review of the literature on nesidioblastosis in pancreatic ectopic tissue and to describe a case of the co-occurrence of these 2 rare conditions. CASE REPORT A 32-year-old man presented with adrenergic and neuroglycopenic symptoms, with laboratory-confirmed hyperinsulinemic hypoglycemia. There was no evidence of tumors on abdominal CT scan and MRI. Celiac trunk sampling with a calcium stimulation test was done, which showed an insulin gradient in the gastroduodenal artery. However, the intraoperative ultrasound showed a small nodule located at the pancreatic tail, leading to distal pancreatectomy. The histologic examination showed nesidioblastosis associated with pancreatic heterotopia. The patient remained asymptomatic after distal pancreatectomy. CONCLUSIONS Nesidioblastosis accounts for 0.5%-5% of all cases of PHH, with a histology showing hypertrophy and hyperplasia of pancreatic islets. Pancreatic heterotopia is a rare congenital anomaly resulting from failure of pancreatic cell migration, and is found as an incidentaloma in imaging or surgeries. Although it is a rare disease, nesidioblastosis should be considered in the investigation of hypoglycemia, even in the rare presentation of nesidioblastosis in patients with pancreatic heterotopy.