An 80-year-old man was admitted to our hospital for repeated tarry stools and hemorrhage. He was taking aspirin and warfarin for atrial fibrillation and obstruction of the central retinal artery. Upper gastrointestinal endoscope revealed a large blood clot at the distal duodenum; however, further insertion was difficult. Insertion of a colonoscope attached with a transparent hood from the mouth enabled the visualization of the third portion of the duodenum. It revealed a large clot, which completely blocked the diverticulum and prevented visualization of the bleeding point. It was extremely difficult to remove the clot through the use of grasping forceps due to poor vision and maneuverability. Finally, the large clot was broken off and removed completely using a snare. The diverticulum was over 20 mm, and a large volume of fresh blood was continuously gushing out from an erosion of the diverticulum. Replacing the tip of the endoscope with a short ST hood and keeping an insulating distance from the bleeding point enabled maneuvering around the steep angles, achieving hemostasis using clips. We report a case of duodenal diverticular bleeding treated endoscopically with great effort in maneuvering to remove a blood clot using snare in a difficult position.