A 22-year-old woman acutely developed recurrent convulsive seizures followed by fever and headache. Cerebrospinal fluid study showed leukocytosis without hypoglycorrhachia. These clinical features suggested acute viral or aseptic encephalitis. The patient was treated only with an antiviral agent and improved immediately with good prognosis. Afterwards, the characteristic brain MRI findings required us to check the patient's serum, and the final diagnosis of myelin oligodendrocyte glycoprotein (MOG) antibody-positive cerebral cortical encephalitis (CCE) was confirmed. Most previously reported cases with MOG antibody-positive CCE clinically showed fever and/or headache, and some were initially misdiagnosed of having central nervous system infection. All previously reported cases were treated with immunotherapy. However, our case showed the very benign clinical course and improved rapidly without any immunotherapy. We should be reminded that MOG-antibody-positive CCE could be self-remitting and mimic acute viral or aseptic encephalitis. In addition, the characteristic neuroradiological findings could be an important clue to the correct diagnosis of CCE.