Segmental colitis associated with diverticulosis (SCAD) is a rare entity characterized by segmental circumferential colonic wall thickening involving the sigmoid and/or left colon in the presence of colonic diverticulosis. We present the case of a 57-year-old female with a past medical history of colonic diverticulosis who presented with chronic intermittent abdominal pain, non-bloody diarrhea, and hematochezia. Imaging revealed long-segment circumferential colonic wall thickening involving the sigmoid and distal descending colon with engorged vasa recta without significant inflammation around the colon or diverticula, consistent with SCAD. Colonoscopy showed diffuse mucosal edema and hyperemia of the descending and sigmoid colon with easy friability and erosions primarily affecting the inter-diverticular colonic mucosa. Pathology showed changes of chronic colitis including inflammation in the lamina propria, crypt distortion, and granuloma formation. Treatment with antibiotics and mesalamine was initiated with improvement in symptoms. This case highlights the importance of considering segmental colitis associated with diverticulosis in patients with chronic lower abdominal pain and diarrhea in the setting of colonic diverticulosis, and the need for a thorough workup including imaging, colonoscopy, and histopathology to differentiate it from other types of colitis.