Objective Hydrocephalus is a common complication of aneurysmal subarachnoid hemorrhage (aSAH), requiring permanent cerebrospinal fluid (CSF) diversion in up to two thirds of patients. Factors that predict permanent CSF diversion are not well established. Methods An exploratory analysis of 149 patients enrolled in the CARAS (Cerebral Aneurysm Renin Angiotensin System) study was performed in an effort to identify factors predictive of permanent CSF diversion after aSAH; only the 135 patients surviving the initial hospitalization were included in the present study. CARAS was a prospective, multicenter study investigating the impact of genetic polymorphisms in patients with aSAH and enrolled patients from September 2012 to January 2015. Results One hundred and forty-nine patients with aSAH were enrolled in CARAS, with 135 (90.6%) patients surviving the initial hospitalization. Sixty-four of these patients (47.4%) required permanent CSF diversion. Multivariable analysis identified the following as independent risk factors: sympathomimetic illicit drug use, external ventricular drain (EVD) insertion, and hyponatremia. A scoring system based on EVD insertion (2 points), Hunt and Hess grade (1 point if grade ≥4) and modified Fisher computed tomography grade (1 point if grade 4) produced an area under the curve of 0.8 (P < 0.001). Conclusions Sympathomimetic illicit drug use, EVD insertion, and hyponatremia are the strongest predictors of shunt insertion in patients with aSAH. Moreover, a scoring system based on EVD insertion, Hunt and Hess grade, and modified Fisher computed tomography grade can reliably predict the need for shunt placement in patients with aSAH.