BackgroundGastrointestinal stromal tumors are a subtype of mesenchymal tumors. In recent years a significant progress was made in their diagnosis and treatment which led to significant improvement of their prognosis. Endoscopy remains one of the main diagnostic methods. In the rare instance of colonoscopy failure, different approaches are available: different endoscope, computed tomography colonography, capsule endoscopy, use of an enteroscope.Case presentationWe present the case of a 75-year-old Caucasian man admitted for abdominal pain, diarrhea and weight loss. Two colonoscopy attempts failed in a different center and a decision to use colon capsule endoscopy was made. This exam revealed a submucosal mass located in the sigmoid colon. Surgery was performed and a local invading gastrointestinal stromal tumor was removed. This is the first image of a colonic gastrointestinal stromal tumor seen on capsule endoscopy.ConclusionColon capsule is a useful diagnostic tool in selected patients after colonoscopy failure or contraindication.