A 6-month-old, female, intact Rottweiler dog was presented to the Iowa State University Veterinary Teaching Hospital for a progressive history of abnormal behavior and generalized ataxia. At necropsy, there was eosinophilic infiltration of the brain and spinal cord, most severe in the medulla oblongata, cerebellum, and cervical spinal cord. Infiltrates of eosinophils were also present in the liver and small intestines. The dog was diagnosed with idiopathic eosinophilic meningoencephalomyelitis based on cerebrospinal fluid analysis, histopathology, and special stains to exclude etiologic agents.