Postoperative duodenal fistulas are associated with high morbidity, particularly in patients with surgically altered anatomy. We report successful endoscopic management of a complex duodenal fistula in a 69-year-old man with prior Billroth II gastrectomy, complicated by colon cancer–related duodenal perforation after surgery. Persistent high-output fistula following two surgical revisions prompted a multidisciplinary endoscopic rescue approach. Using a duodenoscope, biliary and pancreatic ducts were selectively cannulated and plastic stents placed with distal ends in the gastric remnant to divert bile and pancreatic secretions away from the fistula. A fully covered enteral metal stent was deployed across the duodenal defect, combined with continuous nasoduodenal suction drainage. Drain output progressively resolved. Four-week follow-up imaging confirmed fistula closure, allowing safe removal of all devices.