A 6-year-old male Boxer dog was presented with a history of acute blindness. Direct and consensual pupillary light reflexes were reduced. The fundus of both eyes appeared normal during ophthalmoscopic examination. Further diagnostic investigations included magnetic resonance imaging of the brain and electroretinography. Magnetic resonance imaging of the brain was normal, but the electroretinogram was extinguished. A diagnosis of sudden acquired retinal degeneration was made.