Transient mutism after posterior fossa surgery in children or associated with cerebellar hemorrhage or trauma is a recognized phenomenon. However, its association with parainflammatory cerebellitis has been rarely described. We report on a previously healthy 3-year-old child with severe cerebellitis after acute gastroenteritis of unidentified cause. Severe ataxia and transient mutism were the prevailing clinical features. Magnetic resonance imaging revealed swelling of the cerebellum with protruding cerebellar tonsils at the level of the occipital foramen. Recovery from the acute illness was slow and incomplete. Residual cerebellar dysfunction manifested with dysphonic and dysarthric speech, as well as motor coordination problems and was associated with atrophy of the vermis and cerebellar hemispheres in follow-up studies.