A 68-year-old immunosuppressed woman was admitted with poor-functioning colostomy, which she had following a Hartmann’s procedure for diverticular disease in sigmoid colon 8 years previously. She was on cyclosporin and warfarin for transplanted kidney and atrial fibrillation, respectively. On admission, an erythematous and tender swelling was found around the stoma, which was diagnosed as an irreducible, parastomal hernia clinically. The swelling was investigated further with CT, which revealed an organised mesocolic abscess of diverticular origin. The abscess was drained percutaneously under radiological guidance. She recovered well subsequently. This case is a unique presentation of diverticular abscess and management was a challenge considering the patient’s co-morbidities and the location of the abscess.