Duplication of the gastrointestinal tract is a rare congenital surgical malformation. The frequency of the anomaly is 1:4500 ofnewborns, the most frequent localization of the duplication is the iliac region of the small intestine – 33%, duplications of the jejunum make up 7-10% of the total number of cases. The complexity of diagnosis and choice of surgical tactics is due to the absence of specifi c symptoms, possible asymptomatic presence for a long time, clinical manifestations characteristic of other diseases. The article presents an example of a clinical case of doubling of the jejunum in a pediatric patient complicated by peptic ulcer and diff use peritonitis. Complaints, features of the diagnostic process at the prehospital stage, selected surgical tactics, and causes of complications were analyzed.Morphologic signs of jejunal duplication are given. The given clinical example proves that the cause of dyspeptic phenomena of long duration and abdominal pain of unknown origin in pediatric patients may be surgical pathology, in particular, doubling of the gastrointestinal tract complicated by infl ammation of the small intestine. Therefore, such patients need the consultation of a pediatric surgeon, search and detection of possible surgical pathology, including doubling of the intestine. The diagnostic methods for detecting this anomaly are radiography, ultrasound, and contrast- enhanced computed tomography (CECT). Perforation in GI duplication is one of the causes of peritonitis that should be considered by emergency pediatric surgeons in their practice. Timely determination of the patient’s gastrointestinal tract duplication allows the emergency surgeon to optimize diagnostic measures, optimal choice of surgical approach, predict the volume of surgical intervention, avoid possible complications, reduce the time and cost of treatment. Since the fi nal confirmation of the diagnosis of gastrointestinal tract duplication is the result of morphological examination, its performance is mandatory.