The endoscopic diagnosis of autoimmune pancreatitis from histologic criteria remains challenging as it requires adequate architectural details rather than cytology alone. A 67-year-old man presented with progressive abdominal pain and weight loss. Cross-sectional imaging showed inflammatory changes of the pancreatic body and tail and periaortitis on abdominal computed tomography, but normal serum immunoglobulin G4. A mass-like lesion of the pancreatic body and tail was identified on endoscopic ultrasonography. A histologic diagnosis of autoimmune pancreatitis was accomplished through needle biopsy using a novel fork-tip needle.