Acute Disseminated Encephalomyelitis (ADEM) is an inflammatory disease that causes demyelination and affects the white matter of the brain and spinal cord through an immune response. The patient, an eight-year-old Iranian Kurdish boy with a height of 125 cm and a weight of 24 kg, complained from fever for three days which didn’t respond to acetaminophen medication. After three days, the symptoms developed into headache, vomiting, and decreased consciousness. The patient was admitted to the emergency department of Imam Hasan hospital in Bojnourd, Iran, in July 2019. LP diagnostic testing, Wright Agglutination test, Brain CT, and MRI examination were performed. Finally, a diagnosis of acute disseminated encephalomyelitis (ADEM) was confirmed. Following the ADEM diagnosis, methylprednisolone 500 mg was administered immediately and continued for five days. This case study suggests that MRI is the most effective method of diagnosis for ADEM, and high-dose methylprednisolone is the treatment of choice for this syndrome.