A great white pelican (Pelecanus onocrotalus) was referred for assessment of a subacute-onset, nonpainful swelling located in the pectoral region. Physical examination revealed a firm, round, well-circumscribed subcutaneous mass approximately 10 cm in diameter. Cytological evaluation of a fine needle aspirate of the mass was consistent with a mesenchymal tumor. The mass was excised, and a diagnosis of xanthomatosis was made based on histopathologic results. Avian xanthomatosis is a nonneoplastic condition of unknown etiology. Possible causes of this condition include trauma, metabolic or nutritional disorders. Similar lesions were not observed in the nine conspecifics that were fed the same diet and housed in the same enclosure. To our knowledge, this is the first report of xanthomatosis in the family Pelecanidae.