The most common cause of acquired hydrocephalus in infants is hemorrhage, most often as a consequence of prematurity. Other important causes include neoplasm and infection, usually bacterial meningitis. Hypoxic ischemic encephalopathy (HIE) in term infants usually results in secondary microcephaly. We report an infant with severe HIE at birth treated by therapeutic hypothermia who developed progressive acquired hydrocephalus over 2 months, although no cause of the hydrocephalus was identified. Although hydrocephalus, even intraventricular hemorrhage, is uncommon in term infants with HIE, careful follow-up of the head circumference is important, even if no findings indicating possible causes of hydrocephalus, such as hemorrhage, are detected on ultrasound or magnetic resonance imaging.