A 72-year-old woman presented with massive hematochezia. Colonoscopy revealed active bleeding from a diverticulum in the ascending colon, diagnosed as colonic diverticular hemorrhage. Endoscopic band ligation (EBL) was performed for the hemostasis. The patient developed abdominal pain in the right lower quadrant 1 day after EBL. Computed tomography (CT) demonstrated dirty fat around the ascending colon and thickened peritoneum without perforation or abscess formation, consistent with uncomplicated diverticulitis. The patient was discharged with intravenous antibiotic therapy 5 days after EBL. Attention should be given to the occurrence of colonic diverticulitis after EBL for colonic diverticular hemorrhage.