ABSTACT Background: Gastrointestinal stromal tumors (GIST) are the most common mesenchymal neoplasms of the digestive tract. They are believed to originate from the interstitial cells of Cajal or their precursors. Case Report: A 10-day-old boy presented with intestinal obstruction. He was operated upon and a mass was found at the sigmoid colon, which was resected and divided colostomy was performed. The diagnosis of neonatal GIST was confirmed by histologic and immunohistochemical studies. Conclusion: This is the ninth case of neonatal GIST that arose from the intestine and the first reported to arise from the sigmoid colon. Colonic GIST can occur in the neonatal age group.