Mumps is still one of the most common childhood diseases in areas where national immunization has not been implemented. Although central nervous system manifestation is not so uncommon, hydrocephalus secondary to mumps is very rare. In this report, we present a toddler who developed severe hydrocephalus during mumps infection, which resolved via timely cerebral spinal fluid (CSF) drainage. We would like to emphasize early intervention for CSF external drainage.