Objective: Subarachnoid hemorrhage (SAH) is a severe neurological condition often associated with elevated intracranial pressure (ICP), which can impact patient outcomes. The present study aimed to evaluate the prognostic significance of ICP thresholds in predicting prognosis in SAH patients. Methods: A retrospective cohort study was conducted, including patients diagnosed with SAH who underwent ventriculostomy between January 2019 and December 2024. Prognostic factors were estimated from various clinical-radiographic characteristics and ICP using the Cox regression model. Additional analyses were performed to evaluate the relationship between ICP thresholds and hazard ratio by dose-response analysis. Results: A total of 110 SAH patients were included in the study. The analysis demonstrated a significant association between elevated ICP and poor outcomes (Hazard ratio (HR) 1.06, 95% CI 1.03–1.09). In multivariable analysis, ICP value was significantly associated with prognosis when the model was adjusted with pupillary light reflex (HR 1.04, 95% CI 1.01–1.08). In addition, SAH patients were divided into two groups based on the ICP cutoff value of 24 mmHg. Consequently, the group with ICP values of 24 mmHg or higher was strongly associated with poor prognosis (p-value of log-rank test=0.01). Conclusions Our study demonstrates that elevated ICP, particularly beyond the threshold of 24 mmHg, is strongly associated with poor outcomes in SAH patients. These findings support the inclusion of ICP thresholds in prognostic assessment and underscore the need for vigilant ICP monitoring and early intervention in the neurocritical care setting.