Thiopurine-based drugs such as azathioprine and 6-MP are among the most common immunosuppressants used to treat inflammatory bowel disease, autoimmune hepatitis, various autoimmune diseases, and patients undergoing organ transplantation. The drugs are associated with various complications, of which one of the most serious is hepatotoxicity that may trigger non-cirrhotic portal hypertension. We report a case with this side-effect in a patient taking azathioprine to treat Crohn’s disease. (Korean J Med 2020;95:119-123)