There is presented the clinical report of the diagnosis and surgical treatment of such rare malformation as tubular duplication of the small intestine in an 11-years girl. Clinical manifestations were intense abdominal pain and intestinal bleeding of unknown origin. Video capsule enteroscopy (VCE) made it possible to identify the pathological area and determine its location. The article presents modern ideas about duplication of the small intestine. There are indicated diagnostic methods and signs to allow suspecting this malformation. The possibilities and criteria for VCE in diagnosing subepithelial lesions and identifying the source of intestinal bleeding are described.