Several case reports have described severe postoperative enteritis shortly after total colectomy for ulcerative colitis. The very low incidence of this condition makes diagnosis and treatment difficult, and the appropriate treatment strategy is unclear. We report two cases of enteritis after surgery for ulcerative colitis, which were treated with anti-tumor necrosis factor-α therapy. Case 1 involved a 22-year-old man with symptoms, such as nausea 40 days after total colectomy. Gastrointestinal endoscopy revealed patchy obliteration of the vascular pattern, erosions in the duodenum, and superficial ulcers in the small intestine. His symptoms and endoscopic findings immediately improved upon administration of infliximab; clinical remission lasted 5 years with continuous administration. Case 2 involved a 64-year-old man, who had a large amount of watery diarrhea from ileostomy that increased 5 days after total colectomy; gastrointestinal endoscopy revealed extensive ulcers in the small intestine. Symptoms and endoscopic findings improved with prednisolone, but relapsed with tapering of the corticosteroid. Administration of adalimumab resulted in marked improvement of enteritis. However, the small intestine developed a pinhole stricture, and partial resection of the small intestine was performed. Our experience with two cases indicates that anti-tumor necrosis factor-α therapy may play an important role in ulcerative colitis-related postoperative enteritis.