Duodenal duplication cyst (DDC) is a rare form of intestinal malformation (2—12% of all gastrointestinal duplications). There are many difficulties in diagnosis and management of DDC. We present a case of successful endoscopic transluminal treatment of DDC in a 30-year-old female. She complained of epigastric pain, nausea and vomiting, weight loss of 5 kg over the past 3 months. Laparoscopic cholecystectomy for gallstone disease was performed 18 months prior to admission. Examination revealed a cyst 52×60?35 mm in descending part of duodenum. There was a calculus inside the cyst. Transluminal endoscopic cyst fenestration was performed. Histological examination confirmed DDC. According to control duodenoscopy data, cyst was collapsed. The patient remains asymptomatic three months after surgery. DDC is a rare disease of gastrointestinal tract, which should be differentiated first with choledochocele Todani type III and intraluminal duodenal diverticulum. Endoscopic treatment may be an adequate alternative to traditional interventions in some cases.