Description: A 17-year-old, male castrated cougar (Puma concolor) was presented minimally responsive and severely depressed, with bilateral mydriasis and absent pupillary light response. On gross examination of the brain, there was a tan-to-gray, invasive mass with a central cavitation on the ventral aspect in the left cerebral hemisphere, rostral to the caudate nucleus. On histopathologic examination, the mass was composed of sheets of medium-sized, round-to-polygonal cells that were multifocally separated by islands of neuropil. Approximately 80 percentage of the neoplastic cells showed strong cytoplasmic labeling for glial fibrillary acidic protein. These findings were consistent with a medium-grade astrocytoma. To the authors` knowledge, neoplastic disease of the central nervous system has not been previously reported in cougars