A seven-year-old neutered male Labrador retriever was presented with behavioral changes and reducedvision. Neurological examination revealed blindness of the left eye with a positive pupillary lightreflex and a decreased mental status. Blood and cerebrospinal fluid analyses showed no abnormalities.MRI revealed a deviant area located in the thalamic, hypothalamic and caudate nuclear regions. Invasionof the left optic nerve was also observed. The dog was euthanized after 38 days of palliative treatment.Necropsy showed a non-encapsulated extruding white lardaceous mass, with a diameter of 2 cm,in the white matter, located in the ventral thalamic region near the chiasma opticum, which extended alongthe left optic nerve. Histologically, neoplastic cells had a “fried egg” appearance. Immunolabelling forglial fibrillary acidic protein demonstrated the presence of numerous reactive astrocytes. The tumor wasdiagnosed as a low grade (II) intracranial oligodendroglioma with infiltration of the optic nerve.