A 72-year-old man with diabetes mellitus and hypertension was admitted for further examination and therapy of diabetes. In order to evaluate his pancreas, abdominal computed tomography (CT) was performed, showing a space-occupying lesion (SOL) in the pancreatic uncus. He did not show any symptoms related to the pancreas or gastro intestinal tract. Three-dimensional CT (3D-CT) indicated that the SOL was not a solid tumor but a vessel fistula, fed by the superior mesenteric artery and the gastro duodenal artery, drained by the superior mesenteric vein. Abdominal angiography also showed its peculiar vessel structure, confirming arterio-venous (A-V) malformation in the pancreas. Pancreatic A-V malformation is a rare condition but should not be forgotten in the differential diagnosis of pancreatic SOL. Our case showed the advantages of 3D-CT with its low invasiveness and convenience for the diagnosis of A-V malformation in the pancreas.