A 28 year-old man with ulcerative colitis treated for 10 years with azathioprine (AZA) returned from Central Asia with fever, swollen lymph glands, hepatosplenomegaly, and pancytopenia. He was tested positive for acute Epstein-Barr virus (EBV) infection. Before the final diagnosis of EBV-associated large B-cell lymphoma was confirmed, he died from multiple organ failure. AZA and 6-mercaptopurine are associated with the development of EBV-positive lymphomas in organ-transplanted patients. This type of lymphoma is a rare complication in inflammatory bowel disease.