Purpose: In pediatric, head trauma acute hydrocephalus is an uncommon but possible complication. Association with a subarachnoid hemorrhage is poorly described. Methods: We described a case of an 8-year-old girl with acute hydrocephalus secondary to peri-mesencephalic subarachnoid hemorrhage after mild head trauma resolved with external ventricular drainage. Furthermore, we have conducted a review of the literature about this complication in pediatric head trauma. Discussion and conclusion: Acute hydrocephalus related to post-traumatic peri-mesencephalic subarachnoid hemorrhage (tSAH) is an unknown entity in pediatric head trauma. According to our experience, traumatic peri-mesencephalic SAH should be under close clinical monitoring to identify post-traumatic hydrocephalus (PTH), a potentially fatal complication in pediatric mild head trauma. [ABSTRACT FROM AUTHOR]