We report a 7-year-old boy with a history of headaches, staring spells and speech delay. His neurological examination showed difficulties with tandem gait but no other cerebellar signs. Head CT showed an incidental mass suggestive of large arachnoid cyst of the posterior fossa. Brain MRI showed a cystic lesion at the inferomedial aspect of the left cerebellar hemisphere that follows CSF on all sequences and measured 5.3 cm transverse × 4.1 cm AP × 3.4 cm craniocaudal also consistent with an arachnoid cyst. The posterior wall of the cyst was then resected to create an opening end of the cyst. The symptoms improved but the procedure was complicated days later with the development of pseudomeningocele, a rare complication in children.