The groove area is localized between the head of the pancreas, the duodenum, and the common bile duct. Differentiating of groove pancreatitis from pancreatic carcinoma is often difficult. Herein, we report a 54-year-old woman with groove pancreatic adenocarcinoma presenting epigastralgia, jaundice, and vomiting. The diagnosis was confirmed by computed tomography (CT), endoscopic retrograde cholangiopancreatography (ERCP), and endoscopic biopsy. The patient underwent pancreatoduodenectomy. Microscopically, well-differentiated adenocarcinoma was mainly located in Santorini's duct, but there was no invasion to the main pancreatic duct. The patient followed a satisfactory post operative course. She is doing well without recurrence 15 months after the surgery. It is very difficult to differentiate groove pancreatic carcinoma from groove pancreatitis. To avoid unnecessary surgical treatment, endoscopic biopsy and observation of the duodenum are useful for diagnosis. However, keeping in mind the differential diagnosis of pancreatic head carcinoma is necessary.