Gastrinoma is a hormone-secreting tumor associated with the Zollinger-Ellison syndrome. It is quite rare among children, and it is also uncommon in locations other than the pancreas and the duodenum in the pediatric group. Here, we describe an adolescent male, presenting with recurrent secretory diarrhea and abdominal cramping pain, who had a solitary gastrinoma in the lesser sac, close to the stomach. The prognosis was good after complete resection.