Background: A decompressive craniectomy (DC) is a surgical procedure sometimes utilized to manage refractory intracranial hypertension following severe traumatic brain injury (sTBI). The previous studies have established a relationship between DC and post traumatic hydrocephalus (PTH). This study aimed to identify the factors responsible for developing shunt-amenable PTH in patients who underwent DC following sTBI. Methods: A review of a prospectively collected database of all patients admitted with severe TBI in a tertiary neurosurgical center in North-west England between January 2012 and May 2022 was performed. PTH was defined as evidence of progressive ventricular dilatation, clinical deterioration, and/or the eventual need for cerebrospinal fluid diversion (i.e., a ventriculoperitoneal shunt). Statistical analysis was carried out using IBM SPSS versus 28.0.1. Results: Sixty-five patients met the eligibility criteria and were included in the study. The mean age of the PTH group was 31.38 ± 14.67, while the mean age of the non-PTH group was slightly higher at 39.96 ± 14.85. No statistically significant difference was observed between the two groups’ mechanisms of traumatic injury (P = 0.945). Of the predictors investigated, cerebellar hematoma (and contusions) was significantly associated with PTH (P = 0.006). Conclusion: This study concludes that cerebellar hematoma (and contusions) are associated with developing PTH in patients undergoing DC.