Duodenal diverticulum usually originates in the second portion of the duodenum and occasionally causes duodenal obstruction, hemorrhage, perforation and diverticulitis. A bleeding from Dieulafoy's lesion in a duodenal diverticulum is rare. It is not easily dignosed and treated by forward viewing endoscopy. Recently, a case was reported describing the hemorrhage from the Dieulafoy's lesion in a duodenal diverticulum which was treated by hemoclip with forward viewing endoscopy. Hemoclip application is considered to be the most appropriate endoscopic treatment, because sclerotherapy, electrocoagulation or band ligation for Dieulafoy's lesion in the duodenal diverticulum may increase risk of duodenal perforation. We report a case of duodenal perforation due to hemoclip application for the treatment of Dieulafoy's lesion in a duodenal diverticulum.