Kaposi's sarcoma is an unusual tumor principally affecting the skin of the lower extremities. Although the association between Kaposi's sarcoma and renal transplant has been well documented, there are few Kaposi's sarcoma cases in the literature associated with ulcerative colitis or other inflammatory bowel diseases. This report presents a patient with ulcerative colitis who developed Kaposi's sarcoma following treatment with long-term medium-dose azathioprine and additional corticosteroids. Kaposi's sarcoma is a rare complication in inflammatory bowel diseases that may (or may not) be related to immunosuppression. Hence, immunomodulatory agents should be planned carefully in the treatment of inflammatory bowel diseases and avoided if they are not essentially necessary. Cases of colorectal Kaposi's sarcoma complicating inflammatory bowel disease should be managed with a conservative approach and discontinuation of the immunosuppressive treatment.