Nesidioblastosis in one of the causes of hyperinsulinemic hypoglysemia in infancy. The most important goal of treatment for persistent hypoglycemia is the prevention of permanent brain damage. The early surgical management is satisfactory to this goal in nesidioblastosis and maintains normal blood sugar level without administration of drugs or supplement of sugar postoperatively in many cases. We experienced a female infant of 3 months old who has suffered from persistent hypoglysemia due to hyperinsulinism and was suspected nesidioblastosis for its cause clinically. She underwent 95% distal pancreatectomy. The histologic findings of nesidioblastosis was confirmed postoperatively. No postoperative complication was occured and her blood sugar levels were maintained within normal range without medical treatment.