Diverticulitis and diverticular abscesses are rare and potentially serious complications of duodenal diverticulum. These conditions often lead to perforation of the diverticulum, necessitating surgical treatment. There have been few reported cases of duodenal diverticulitis with or without perforation treated by endoscopic drainage. Here, we present a case of duodenal diverticulitis accompanied by abscess formation that was treated successfully with an endoscopic nasobiliary drainage catheter. We suggest this treatment could be an acceptable option for selected patients with a localized abscess that is resistant to conservative treatment.