A 52-year-old male with prior right hemicolectomy for colorectal cancer underwent endoscopic resection of a large duodenal adenoma involving 95% of the luminal circumference in the third duodenal part. Circumferential (360°) resection of the lesion was followed by partial closure of mucosal defect using Mantis and TTS clips. Focal capillary bleeding was controlled with a hemostatic coagrasper and adjunctive hemostatic powder. A post procedural CT scan revealed a small volume of peri-duodenal air and fluid, which resolved spontaneously without the need for intervention. Scheduled surveillance endoscopies at 20, 30 and 40 days after resection were performed and included circumferential submucosal triamcinolone injection to prevent post-procedural stenosis. This was well tolerated and effectively prevented lumen narrowing, with maintained patency on follow-up.