Objective: To assess the prevalence of acute kidney injury in patients with subarachnoid hemorrhage patients., Design: Retrospective analysis of all subarachnoid hemorrhage admissions., Settings: Neurocritical care unit., Patients: All patients with a diagnosis of subarachnoid hemorrhage between 2009 and 2014., Interventions: None., Measurements and Main Results: Of 1,267 patients included in this cohort, 16.7% developed acute kidney injury, as defined by Kidney Disease Improving Global Outcome criteria (changes in creatinine only). Compared to patients without acute kidney injury, patients with acute kidney injury had a higher prevalence of diabetes mellitus (21.2% vs 9.8%; p < 0.001) and hypertension (70.3% vs 50.5%; p < 0.001) and presented with higher admission creatinine concentrations (1.21 ± 0.09 vs 0.81 ± 0.01 mg/dL [mean ± SD], respectively; p < 0.001). Patients with acute kidney injury also had higher mean serum chloride and sodium concentrations during their ICU stay (113.4 ± 0.6 vs 107.1 ± 0.2 mmol/L and 143.3 ± 0.4 vs 138.8 ± 0.1 mmol/L, respectively; p < 0.001 for both), but similar chloride exposure. The mortality rate was also significantly higher in patients with acute kidney injury (28.3% vs 6.1% in the non-acute kidney injury group [p < 0.001]). Logistic regression analysis revealed that only male gender (odds ratio, 1.82; 95% CI, 1.28-2.59), hypertension (odds ratio, 1.64; 95% CI, 1.11-2.43), diabetes mellitus (odds ratio, 1.88; 95% CI, 1.19-2.99), abnormal baseline creatinine (odds ratio, 2.48; 95% CI, 1.59-3.88), and increase in mean serum chloride concentration (per 10 mmol/L; odds ratio, 7.39; 95% CI, 3.44-18.23), but not sodium, were associated with development of acute kidney injury. Kidney recovery was noted in 78.8% of the cases. Recovery reduced mortality compared to non-recovering subgroup (18.6% and 64.4%, respectively; p < 0.001)., Conclusions: Critically ill patients with subarachnoid hemorrhage show a strong association between hyperchloremia and acute kidney injury as well as acute kidney injury and mortality.