Head injuries in infants are very common and usually asymptomatic. We report an eleven-month old female, who suffered repeated episodes of emesis caused by a mild head trauma. At the admission, the girl was neurologically intact, but she quickly became deteriorated and drowsy, presenting the setting sun sign. Brain CT scan revealed acute obstructive hydrocephalus at the level of the aqueduct. Even though there was no evidence of intraventicular hemorrhage, we urgently performed an external ventriculostomy in order to control her intracranial hypertension. Afterwards, the neurological signs, as well as the imaging findings, were rapidly improved. Two years follow-up revealed an absolutely normal psychomotor development of the child. To conclude, transient acute obstructive hydrocephalus in children is an uncommon entity and its pathogenesis remains unclear. However, a mild head trauma could be the underlying pathogenic mechanism for this rare clinicopathological entity.