This is a report of a case following an 8 year old male neutered Golden Retriever through his diagnosis of an Oligodendroglioma and the resultant procedures and treatment. The patient presented to Cornell’s Oncology Service for consultation on external beam radiation therapy for a previously diagnosed brain tumor. He was a healthy dog with no prior medical conditions until two months prior when he experienced his first seizure. One month later, a second seizure was observed. He was brought to a veterinarian where an MRI showed a 3 cm x 3 cm mass in his right occipital lobe adjacent to the fourth ventricle, which was compressing his midbrain; no other abnormalities were found on further screening (complete blood count, chemistry panel, and thoracic radiographs). Two weeks later, surgery was performed to remove the mass. The mass was sent for histopathology, which came back as a presumptive oligodendroglioma. He was then referred to Cornell for external beam irradiation following surgery. His physical exam was normal and there were no significant abnormalities found on blood work. A CT scan for radiation therapy planning was performed which unexpectedly showed a mass effect in the right occipital lobe in the same location as seen previously prior to surgery. The owner elected for a glioma clinical trial at the University of Minnesota. There the patient underwent surgery to remove the mass, of which complete removal was documented on a post op MRI. This was followed with immunotherapy. He did well until five months post diagnosis when he began to have cluster seizures which were only able to be controlled under sedation. He was humanely euthanized. A post mortem MRI did not show any mass evidence of tumor regrowth but the final necropsy report is still pending.