OBJECTIVE Improved outcomes in patients with subarachnoid hemorrhage (SAH) treated at high-volume centers have been reported. The authors sought to examine whether hospital case volume and comprehensive stroke center (CSC) capabilities affect outcomes in patients treated with clipping or coiling for SAH. METHODS The authors conducted a nationwide retrospective cohort study in 27,490 SAH patients who underwent clipping or coiling in 621 institutions between 2010 and 2015 and whose data were collected from the Japanese nationwide J-ASPECT Diagnosis Procedure Combination database. The CSC capabilities of each hospital were assessed by use of a validated scoring system based on answers to a previously reported 25-item questionnaire (CSC score 1–25 points). Hospitals were classified into quartiles based on CSC scores and case volumes of clipping or coiling for SAH. RESULTS Overall, the absolute risk reductions associated with high versus low case volumes and high versus low CSC scores were relatively small. Nevertheless, in patients who underwent clipping, a high case volume (> 14 cases/yr) was significantly associated with reduced in-hospital mortality (Q1 as control, Q4 OR 0.71, 95% CI 0.55–0.90) but not with short-term poor outcome. In patients who underwent coiling, a high case volume (> 9 cases/yr) was associated with reduced in-hospital mortality (Q4 OR 0.69, 95% CI 0.53–0.90) and short-term poor outcomes (Q3 [> 5 cases/yr] OR 0.75, 95% CI 0.59–0.96 vs Q4 OR 0.65, 95% CI 0.51–0.82). A high CSC score (> 19 points) was significantly associated with reduced in-hospital mortality for clipping (OR 0.68, 95% CI 0.54–0.86) but not coiling treatment. There was no association between CSC capabilities and short-term poor outcomes.