Acute disseminated encephalomyelitis (ADEM) is a monophasic clinical syndrome, characterised by immune-mediated demyelination of the central nervous system. Differentiating ADEM from acute viral encephalomyelitis may pose a difficult clinical challenge. We describe a 3-year-old girl who presented with fever, weakness in all four limbs, urinary retention, respiratory distress and altered sensorium. MRI of the brain showed multiple cerebral T2-hyperintense signals with bilateral thalamic and basal ganglia involvement. MRI of the spine showed extensive T2-hyperintensities from cervical to lumbar spinal cord. Cerebrospinal fluid examination was normal. The patient was diagnosed as ADEM and treated with intravenous methylprednisolone. She showed complete clinical and radiological improvement at the end of 1-month follow-up.