A case of pancreatic acinar cell tumor (ACC) is presented in a 10-year-old boy. The tumor manifested clinically with Cushing's syndrome, high serum adrenocorticotropic hormone (ACTH) and cortisol concentrations. In addition, excessive serum levels of alpha-fetoprotein (AFP) were detected. Surgical resection was not possible due to retroperitoneal invasion. Biopsy of the mass showed a solid, poorly differentiated ACC of the pancreas. Periodic acid Schiff positive cytoplasmic granules, trypsinogen, keratins, alpha-1-antitrypsin, and AFP were identified in the tumor cells. Electron microscopy demonstrated zymogen granules as well as isolated dense core granules. Using immunochemiluminometric assay, a high quantity of ACTH was found in the fresh frozen tumor extract. ACTH, chromogranin A, and corticotropin-releasing factor were identified only in a few cells by immunohistochemistry. Combined radiochemotherapy was temporarily effective in reducing the tumor mass and serum AFP. Serum ACTH and cortisol levels dropped progressively and definitively to normal values after chemotherapy, and the Cushing's syndrome subsided. Two years later, the patient died with metastatic disease. The presented case of ACC is interesting due to high serum AFP values and ectopic ACTH secretion resulting in Cushing's syndrome.