Background Acute cerebellitis is an inflammatory process commonly involving both cerebellar hemispheres. Bilateral cerebellar hemisphere involvement is the most common finding. Acute hemicerebellitis in childhood is an extremely rare unilateral presentation of cerebellitis mimicking a tumor. Its etiology is unknown, although an inflammatory or post infectious origin is presumed. Its clinical outcome is generally good and a self-limited evolution. Clinical improvement and regression of the pathological findings in serial MRI will help differentiate acute hemicerebellitis from a neoplastic process. Case presentation We present a case of hemicerebellitis in a 7-year-old girl, presenting with severe headache, projectile vomiting, and mixed neuropsychiatric manifestation. MRI of the brain revealed a unilateral cerebellar involvement.