A 3.5 month old male Rottweiler presented for a one day history of seizures. The puppy had been previously vaccinated for canine distemper virus and tested negative for canine distemper virus one month prior to presentation. The puppy presented with an obtunded to stuporous mentation, left head tilt, tetraparesis and ataxia, absent menace and miotic pupils OU, mild positional rotary nystagmus, positional left strabismus, delayed proprioception in all limbs, and significant head and cervical pain. Neurolocalization indicated a multifocal lesion involving the forebrain and brainstem. An emergent MRI revealed diffuse severe pachymeningeal contrast enhancement and a cerebrospinal fluid analysis revealed a mixed cell pleocytosis including some eosinophils that cultured negative. Bloodwork, urinalysis and culture were unremarkable and infectious disease titers were submitted. The prioritized differentials for the patient included an infectious or auto-immune meningoencephalitis and treatment was initiated. Despite treatment, the patient's neurologic status declined to the point where his mentation was stuporous to comatose and he developed hyponatremia due to syndrome of inappropriate ADH. The patient became hypothermic and was euthanized. Postmortem diagnostics were positive for a canine distemper virus infection. This report will describe the clinical findings, diagnostics, and treatment in a dog with canine distemper virus and exploring the possibility of a vaccine induced infection.