Thiopurine drugs have been widely used in the treatment of inflammatory bowel disease. However, their use is limited by adverse effect that can lead to cessation of therapy. We report 2 cases of thiopurine-induced acute pancreatitis in patients with inflammatory bowel disease. Both patients complained of abdominal pain, showed elevated pancreatic enzymes, and swollen pancreases on computed tomography. The patients' signs and symptoms resolved uneventfully after withdrawal of the thiopurine drugs. Although the mechanism of thiopurine-induced pancreatitis remains unclear, close monitoring and early recognition of acute pancreatitis is important in the management of new thiopurine users.