The role of pre- and intraoperative procedures for the localization of insulinomas has been extensively debated. We report a case of successful treatment using preoperative selective intra-arterial calcium injection and intraoperative glucose monitoring. A 12-year-old boy with hypoglycemic attacks had a large insulinoma in the head of the pancreas on computed tomography. Preoperative selective angiography combined with arterial stimulation-venous sampling (ASVS) by intra-arterial injection of calcium revealed no other insulinomas in the body and tail of the pancreas. Elevation of serum glucose on intraoperative monitoring confirmed complete enucleation of the insulinoma. Preoperative ASVS can accurately localize an insulinoma, and may help to increase the success rate of surgery and avoid blind pancreatectomy.