Autosomal dominant hyperimmunoglobulin E syndrome (HIES, or Job syndrome) is a rare primary immunodeficiency characterized by elevated immunoglobulin E (IgE), eosinophilia, recurrent skin and pulmonary infections, dermatitis, and connective tissue and skeletal abnormalities. A 26-year-old male with known HIES presented with abdominal pain and diarrhea. Imaging showed sigmoid diverticulitis without abscess or perforation. Conservative management with antibiotics failed, and he developed a peridiverticular abscess, which was percutaneously drained with plans for elective resection. He returned four days later with progression of his diverticulitis, requiring partial colectomy with primary anastomosis. To our knowledge, this is the first case of diverticulitis in HIES. Diverticulitis is rare in younger individuals, raising the possibility that the connective tissue abnormalities of HIES patients may predispose them to colonic diverticula. Although the majority of complications are sinopulmonary and skin infections, diverticulitis should be considered in the differential of intra-abdominal processes in HIES.