Pancreatoblastoma, generally regarded as a pediatric malignant tumor, is rarely found in the adult population. Only 13 adults with pancreatoblastoma, ranging in age from 19 to 68 years, have previously been reported in the world literature. A diagnosis of pancreatoblastoma relies on characteristic histologic features, including epithelial differentiation and, more importantly, squamoid differentiation. Despite aggressive therapy, adults with pancreatoblastoma have a poor outcome. We describe a 78-year-old woman who presented with painless jaundice and was found on abdominal computed tomographic scan to have a 2.7-cm ampullary mass. The patient underwent successful pancreaticoduodenectomy. Pathologic examination of the resected tumor revealed findings characteristic of pancreatoblastoma. The tumor formed acinar and glandular structures, solid areas, and contained many "squamoid corpuscles," a defining feature of pancreatoblastoma. The tumor cells also showed acinar and ductal phenotype by immunohistochemistry. To the best of our knowledge, this case represents the oldest patient with pancreatoblastoma to be described in the literature to date and the first to occur in the ampulla of Vater. We review previously published cases and discuss the clinical and histopathologic features of adult pancreatoblastoma.