A 47-year-old woman was admitted to our hospital with complaints of fever, upper abdominal pain, and back pain. The serum amylase, C-reactive protein (CRP), and IgG (especially IgG4) were elevated, and abdominal computed tomography (CT) revealed diffuse enlargement of the pancreas and pseudocysts. Endoscopic retrograde pancreatography (ERP) revealed diffuse irregular narrowing of the main pancreatic duct. Histopathological examination of the pancreatic tissue showed fibrotic change with lymphocytic infiltration. Based on these findings, we diagnosed this case as a case of autoimmune pancreatitis. This case also fully satisfied the diagnostic criteria for autoimmune pancreatitis established by the Japan Pancreas Society in 2002. Few reports have been published on cases of autoimmune pancreatitis complicated by the formation of pseudocysts in the pancreas. We, therefore, report this case here to emphasize that cases of autoimmune pancreatitis can be complicated by the development of pseudocysts.