We report here a case involving a 14-year-old boy who developed acute disseminated encephalomyelitis following live rubella vaccination. The patient became febrile and began to experience nuchal pain 16 days after the immunization. By 22 days after immunization, he experienced difficulty in walking. By 24 days, he had developed tetraparesis with retention of urine, and total sensory loss below the Th1 dermatomal level. He was febrile at this point and showed nuchal rigidity and Lhermitte's sign. Cerebrospinal fluid examination revealed elevated cell counts, protein level, and myelin basic protein. T2-weighted magnetic resonance imaging detected high intensity lesions in the bilateral cerebral white matter and cervical spinal cord. Following the administration of intravenous corticosteroids, the patient's clinical symptoms improved rapidly.