Background <p>The management of hydrocephalus in pediatric posterior fossa tumors remains highly variable. This study aims to analyze hydrodynamic factors and identify predictors of CSF diversion procedures in children undergoing posterior fossa tumor resection.</p> Methods <p>A retrospective cohort study was conducted with pediatric patients who underwent posterior fossa tumor resections at a single center in Latin America. Poisson regression models were applied to analyze associations with ventriculomegaly, need for cerebrospinal fluid (CSF) diversion, postoperative hydrocephalus, and shunt dependence. Survival outcomes were assessed using Kaplan–Meier curve analysis.</p> Results <p>The study analyzed 135 pediatric patients with posterior fossa tumors. Preoperatively, 71.85% had ventriculomegaly and 36.29% required CSF diversion. Postoperatively, 16.32% required new CSF diversion, and 25.93% remained shunt dependent. Multivariate analysis revealed that younger age, quadrigeminal cistern involvement, and metastasis were predictors of shunt requirement. Pilocytic astrocytomas were less prevalent among patients with hydrocephalus, while PNET/ATRT were more common. Postoperative hydrocephalus was linked to solid tumors, midline location, and metastasis. “Other embryonal tumors” had a 1.4 times higher likelihood of requiring a VPS postoperatively. The degree of tumor resection was not significantly associated with postoperative hydrocephalus. Considering shunt dependence, patients with ependymomas had a 1.56 times higher likelihood of persistent hydrocephalus. The 5-year OS rate was lower in patients with hydrocephalus (69.4% <i>vs</i> 90.7%).</p> Conclusion <p>Tumor resection alone may not suffice to prevent hydrocephalus, particularly in younger children and those with ependymomas. High shunt dependency and related complications highlight the importance of early identification and careful patient selection for CSF diversion.</p>