A 53-yr-old male captive mata mata turtle (Chelus fimbriatus) was examined following sudden death. The animal was in good nutritional, muscular and postmortem condition. The esophageal wall was circumferentially expanded by a discrete, oblong, irregular, tan, and soft contiguous glandlike structure. Histologically, the mass comprised uneven, sometimes cavitated islands of polygonal neoplastic cells consistent with an esophageal adenocarcinoma. In addition, peripheral to the mass, there was glandular epithelial hyperplasia, dysplasia, and multifocal heterophilic and lymphohistiocytic adenitis. Neoplastic cells expressed pancytokeratins; however, they demonstrated no immunoreactivity to vimentin, chromogranin, synaptophysin, and thyroglobulin. Additional findings included multifocal to coalescing areas of cortical fibrosis and membranous glomerulonephritis affecting both kidneys, and a focal hepatocellular adenoma.