A 76-year-old male with severe abdominal pain and a high fever was admitted to our hospital. The patient underwent a therapeutic endoscopic retrograde Cholangiopancreatography (ERCP) procedure one month previously due to acute biliary pancreatitis and a plastic biliary stent (8.5F) was placed. A follow-up computed tomography (CT) scan identified a huge cyst lesion in the body of pancreas, which was initially misdiagnosed as a pseudocyst. The patient progressed to severe sepsis and septic shock soon after admission.