Because the prognosis of high-grade aneurysmal subarachnoid hemorrhage (aSAH), classified as World Federation of Neurosurgical Societies (WFNS) grade IV-V, is generally poor, the functional outcomes of survivors have not been thoroughly explored. The aim of this retrospective cohort study is to determine predictors of functional independence in patients who survive a high-grade aSAH. We retrospectively evaluated consecutive patients with aSAH admitted to a single institution from January 2000 to April 2015. Adult (age ≥18 years) patients with WFNS grade IV-V aSAH were included for analysis. Patients without sufficient baseline data, those who died before discharge, and those without follow-up data were excluded. Univariable and multivariable logistic regression analyses were used to identify factors associated with functional independence, defined as a modified Rankin Scale score of 0-2, at last follow-up. Of the 260 patients with a WFNS grade IV-V aSAH during the study period, 139 met the inclusion criteria. After a mean follow-up of 6.3 months, functional independence was achieved in 73% of high-grade aSAH survivors (101/139 patients) and in 39% of all high-grade aSAH cases (101/260 patients). Only a lack of cerebrospinal fluid shunt placement was found to be an independent predictor of functional independence in the multivariable analysis (odds ratio 0.28 [0.109-0.722]; P = 0.008). Because functional independence can be achieved in the majority of high-grade aSAH survivors, aggressive initial management of high-grade aSAH is warranted. Strategies that reduce the need for permanent cerebrospinal fluid diversion may improve functional outcomes in survivors of high-grade aSAH.