Differential diagnosis between autoimmune pancreatitis (AIP) and pancreatic cancer is often difficult due to similar clinical manifestations and radiological findings. Serum immunoglobulin G4 (IgG4) is a marker to differentiate AIP from pancreatic cancer. Although serum IgG4 can be elevated in 10% of patients with pancreatic cancer, most of serum IgG4 elevation in pancreatic cancer is limited within two times of upper normal limit. Herein, we report a case of pancreatic cancer with markedly elevated serum IgG4 over six times of upper normal limit that needed steroid trial to differentiate from AIP.