The significant histologic overlap between diversion colitis and inflammatory bowel disease (IBD) poses a diagnostic challenge. We aimed to identify histologic features that are characteristic of diverted colon segments among patients with IBD and compare them with histologic features identified in IBD colectomies. Archived slides from resected diverted colon segments from patients with (n = 79) and without (n = 80) IBD and the corresponding prior colectomies (n = 52) of the IBD patients were reviewed. Clinical and endoscopic data were collected, and a series of histologic features were evaluated and graded. Compared to the non-IBD group, IBD patients were more likely to be symptomatic and present with abnormal endoscopic findings (P .05). The severity of inflammatory activity, crypt architectural distortion, mucosal atrophy, transmural inflammation, intramucosal lymphoid aggregates (IMLAs), and transmural lymphoid aggregates (TMLAs) were significantly greater in diverted segments in IBD cases than controls (P .001). The severity of inflammatory activity, IMLAs, TMLAs, and transmural inflammation and the presence of ulcer(s) in the diverted colon segments of IBD patients were associated with the histologic features reflective of IBD activity such as inflammatory activity, transmural inflammation and ulcer(s) in the preceding colectomies (P .05). Diversion colitis developing in the setting of IBD is endoscopically and histologically distinct from that observed among individuals without IBD. Inflammatory activity, presence of ulcer(s), IMLAs, TMLAs, and transmural inflammation in diverted colon segments of IBD patients may, in part, reflect the severity of underlying IBD rather than pure diversion colitis.