A 49-year-old woman presented with fever, weight loss, night sweats, hematochezia, and acid reflux symptoms. Two large, firm cecal lesions were seen at colonoscopy, but multiple biopsies were inconclusive. The patient underwent a right hemicolectomy for a clinical diagnosis of colon cancer. Noncaseating granulomatous inflammation with background lymphocytes, plasma cells, and histiocytes exhibiting emperipolesis were identified. With these histologic features and immunoreactivity for S-100 protein and CD68, a diagnosis of Rosai-Dorfman disease was rendered. Other areas had storiform fibrosis admixed with numerous immunoglobulin G4 (IgG4)-positive plasma cells. Although a few preliminary reports have noted an increased number of IgG4-positive plasma cells in Rosai-Dorfman disease, the relationship between these 2 conditions is unclear. To our knowledge, this is the first case report of a possible association of colonic Rosai-Dorfman disease with an increased number of IgG4-positive plasma cells. Reviews of colonic Rosai-Dorfman disease and IgG4-related sclerosis are presented to heighten awareness of this rare presentation.