Acinar cell carcinoma (ACC) of the pancreas accounts for approximately 1% of all exocrine pancreatic tumours. We report a rare form of ACC in a 66-year-old man. This tumour was revealed by epigastric pain and weight loss. Abdominal computed tomography showed a hypodense, well-demarcated, heterogeneous lesion, in the head of the pancreas, measuring 4.2 cm in diameter. There was a marked dilatation of the main pancreatic duct upstream, with tumour spreading within this duct. The diagnosis of ACC was made on the fine needle aspiration cytology performed during endoscopic ultrasound examination. On the pancreaticoduodenectomy specimen, the dilated main pancreatic duct (2.5 cm in diameter) was filled by an exophytic tumour. Histological examination showed an ACC, with predominant intraductal growth (main and accessory pancreatic ducts), with pancreatic parenchymal and duodenal invasion. Neuroendocrine markers were negative. To our knowledge, this is the second report of an ACC with predominant intraductal spread. These rare forms of ACC can be confused with intraductal papillary-mucinous neoplasms. In our report, fine needle aspiration cytology performed during endoscopic ultrasound examination was a valuable tool in the diagnostic assessment.