Colonoscopy is a good diagnostic tool and facilitates treatment of various colonic diseases. Nevertheless, it can induce many serious complications such as perforation and hemorrhage. Diverticulitis has also been reported as a serious complication of colonoscopy, with an incidence ranging from 0.04% to 0.08%. A 44-year-old male with chronic hepatitis B was presented with general weakness, myalgia, and febrile sensation. After admission for evaluation, pneumonia detected in the left upper and lower lobe and treated. We performed colonoscopy for screening and found multiple colonic diverticula in the right side of the colon. After 48 hours, the patient complained of abdominal pain and febrile sensation. Physical examination revealed tenderness in the right side of the abdomen. Abdomen-pelvis computed tomography showed bowel wall thickening of the cecum and ascending colon and multiple inflamed diverticula at the cecum with pericolic fat infiltration and fluid collection. We diagnosed the patient with acute diverticulitis after colonoscopy. Thereafter, he was treated with bowel rest and broad-spectrum intravenous antibiotics, and recovered. With a review of the relevant literature, we report a case of acute colonic diverticulitis as a complication of colonoscopy.