In January 2007, an 80-year-old man was admitted to our hospital for treatment of a pancreatic tumor. He had been diagnosed with autoimmune pancreatitis (AIP) in December 2003 for which steroid therapy had induced remission. In November 2006, tumor marker levels rapidly increased, and the patient was suspected of having pancreatic cancer based on imaging studies. The diagnosis was later confirmed by endoscopic ultrasound-guided fine-needle aspiration biopsy. Distinguishing AIP from pancreatic cancer is crucial; however, few previous reports have described any cases of pancreatic cancer associated with AIP. While several reports have speculated on the prognosis of AIP, natural courses of the disease remain uncertain. This report emphasizes that AIP can coexist with cancer.