Background. Duodenal duplication cysts (DDC) are rare congenital anomalies of the gastrointestinal tract and periampullary localization with anatomical variants including biliary and pancreatic duct anomalies remains a surgical challenge. Endoscopic treatment of the periampullary DDC (PDDC) communicating with the pancreaticobiliary duct in an 18-month-old girl is presented to discuss the endoscopic treatment options in children. Case. An 18-month-old girl with a normal prenatal ultrasound (US) was asymptomatic until complaining of abdominal pain and vomiting at 10-months of age. Abdominal US revealed a 1.8 × 2 cm cystic mass adjacent to the second part of the duodenum. The amylase and lipase levels were slightly increased while she was symptomatic. Magnetic resonance cholangiopancreaticography (MRCP) showed a thick cyst wall measuring 1.5 × 2 cm at the second part of the duodenum, consistent with DDC that was suspected to be communicating with the common bile duct. Upper gastrointestinal endoscopy confirmed a bulging cyst in the duodenum lumen. The puncture and injection of the cyst with contrast material confirmed the communication of the duplication cyst with the common bile duct. The unroofing of the cyst was performed with endoscopic cautery. The biopsy obtained from the cystic mucosa revealed normal intestinal histology. Oral feeding was initiated six hours after the endoscopy. The patient has been followed for the last 8 months uneventfully. Conclusions. Endoscopic treatment of PDDC with various anatomical variants can be considered an alternative to surgical excision in children.