Balloon-assisted endoscopy enables stable endoscopic maneuverability. Balloon-assisted endoscopic submucosal dissection (BA-ESD) is useful in the treatment of proximal colorectal tumors where scope maneuverability is poor. Herein, we reported a case in which BA-ESD was successfully performed using a long colonoscope with a guidewire, although the lesion could not be reached using the balloon-assisted endoscopy technique with a therapeutic colonoscopy. A 50-year-old man underwent a colonoscopy that revealed a tumor in the ascending colon. BA-ESD was performed using a conventional therapeutic endoscope due to excessive intestinal elongation and poor endoscopic maneuverability. However, the transverse colon loop could not be reduced, and the total colonoscopy failed despite using balloon-assisted endoscopy. The scope was then changed from a conventional colonoscope to a long colonoscope, inserted into the terminal ileum, and the loop was reduced. After the guidewire was placed at the terminal ileum and the long colonoscope was removed, a therapeutic colonoscopy with an overtube was inserted into the ascending colon without reforming the colonic loop, allowing safe BA-ESD.