Since first described in the mid 1990s, there has been burgeoning literature on IgG4-related sclerosing disease. The number of sites that may be involved is ever increasing, with the pancreas, salivary glands, and lymph nodes being the most commonly affected organs. There are no well-documented cases arising in the gastrointestinal tract. In this report, we present the first case to our knowledge of IgG4-related sclerosing disease involving the small bowel with a distinctly unusual clinicopathologic presentation. A previously well 46-year-old woman presented with a 2-year history of intermittent abdominal pain with recent worsening due to small bowel obstruction. Following imaging, which showed jejunitis with surrounding mesenteric inflammatory changes, she proceeded to a segmental small bowel resection. The resected jejunum revealed an isolated, stenosing chronic ulcer associated with a necrotizing mesenteric arteritis. A transmural inflammatory infiltrate rich in IgG4 plasma cells was seen in the wall of the bowel and mesenteric artery. Abundant IgG4 interfollicular plasma cells were also identified in a mesenteric lymph node. The serum IgG4 level was elevated at >800 mg/dL (reference range 8 to 140 mg/dL). Although phlebitis is an almost constant feature of this disease, arteritis is not described other than in the lung and aorta. In this report, we also discuss the diagnostic pitfalls and the differential diagnoses that should be considered when this condition arises in the gastrointestinal tract.