An adult, captive European spotted fallow deer (Cervus dama) was submitted for necropsy due to sudden death. Gross lesions consisted of serosanguinous fluid in the thoracic cavity with multiple, often confluent, nodules covering visceral and parietal pleura. Microscopic examination revealed tubular structures lined by cuboidal cells covering a delicate fibrous stroma. Gross and microscopic morphology was consistent with a mesothelioma.