A 24-year-old woman was transferred to our hospital under suspicion of an exacerbation of her known ulcerative colitis. Colonoscopy revealed an edematous swelling and multifocal discharge of pus throughout the descending colon, concurrent with active ulcerative colitis findings in the rectum and sigmoid colon. Computed tomography showed a thickened wall and multifocal abscesses within the wall of the descending colon. Two weeks after starting antimicrobial therapy, she was discharged home. This is the first case report of multifocal colonic wall abscesses. In order not to increase the risk of serious infection associated with anti-TNF-α therapy, proper qualification and strict monitoring are essential.