Autoimmune pancreatitis (AIP) is a rare form of chronic pancreatitis, characterised by elevated serum IgG4 levels. AIP is associated with many other diseases, including retroperitoneal fibrosis, sclerosing cholangitis, and sialoadenitis. Here, we report an interesting case of a 45-year-old male who presented with haematemesis, melena, and fever, accompanied by hepatosplenomegaly, systemic lymphadenopathy, diffuse swelling of the pancreas, portal hypertension, and multiple enlarged retroperitoneal lymph nodes on abdominal computed tomography (CT). The patient did not have a history of viral hepatitis or cirrhosis. Laboratory testing revealed an elevated IgG (3000mg/dL). He underwent surgery for uncontrolled active upper gastrointestinal bleeding. We found splenomegaly, with a plump pancreas and involved peripheral lymph nodes, so a splenectomy was performed, and the pancreatic tail and some of the lymph nodes were biopsied. All of the resected tissues were infiltrated by large numbers of IgG4-positive plasma cells. Therefore, this patient was diagnosed with AIP associated with portal hypertension, systemic lymphadenopathy, and splenomegaly. The patient received no other treatment after the splenectomy. By the 6-month follow-up, the patient had recovered, the serum IgG had decreased to normal, and enhanced CT showed a normal pancreas. We speculate that splenectomy may be a new method of treating AIP.