Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease of the central nervous system caused by the human polyomavirus JC virus. PML mainly occurs in immunocompromised patients. A 36-year-old man with no evidence of immunosuppresion presented seizures. MRI scans of brain showed multifocal lesions in the cerebral white matters. JC virus DNA was positive in the cerebrospinal fluid examined by JC virus PCR. We report a rare case of PML presenting as viral encephalitis that occurred in a healthy adult person.