Alimentary tract duplications are rare congenital anomalies. We report a case of a 14-year-old boy, who presented with acute abdomen, with features favouring acute appendicitis. Laparotomy revealed perforated ileal duplication cyst. Resection of ileum along with cyst and anastomosis was undertaken, and proximal ileostomy performed. Postoperative recovery was uneventful and ileostomy was reversed successfully. Histopathology revealed the presence of gastric mucosa at the site of perforation.