ImportanceNeurocritical care (NCC) aims to improve the outcomes of critically ill patients with brain injury, although the benefits of such subspecialized care are yet to be determined.ObjectiveTo evaluate the association of NCC with patient-centered outcomes in adults with acute brain injury who were admitted to intensive care units (ICUs). The protocol was preregistered on PROSPERO (CRD42020177190).Data SourcesThree electronic databases were searched (Ovid MEDLINE, Embase, Cochrane Central Register of Controlled Trials) from inception through December 15, 2021, and by citation chaining.Study SelectionStudies were included for interventions of neurocritical care units (NCCUs), neurointensivists, or NCC consulting services compared with general care in populations of neurologically ill adults or adults with acute brain injury in ICUs.Data Extraction and SynthesisData extraction was performed in keeping with PRISMA guidelines and risk of bias assessed through the ROBINS-I Cochrane tool by 2 independent reviewers. Data were pooled using a random-effects model.Main Outcomes and MeasuresThe primary outcome was all-cause mortality at longest follow-up until 6 months. Secondary outcomes were ICU length of stay (LOS), hospital LOS, and functional outcomes. Data were measured as risk ratio (RR) if dichotomous or standardized mean difference if continuous. Subgroup analyses were performed for disease and models of NCC delivery.ResultsAfter 5659 nonduplicated published records were screened, 26 nonrandomized observational studies fulfilled eligibility criteria. A meta-analysis of mortality outcomes for 55 792 patients demonstrated a 17% relative risk reduction (RR, 0.83; 95% CI, 0.75-0.92; P = .001) in those receiving subspecialized care (n = 27 061) compared with general care (n = 27 694). Subgroup analyses did not identify subgroup differences. Eight studies including 4667 patients demonstrated a 17% relative risk reduction (RR, 0.83; 95% CI, 0.70-0.97; P = .03) for an unfavorable functional outcome with subspecialized care compared with general care. There were no differences in LOS outcomes. Heterogeneity was substantial in all analyses.Conclusions and RelevanceSubspecialized NCC is associated with improved survival and functional outcomes for critically ill adults with brain injury. However, confidence in the evidence is limited by substantial heterogeneity. Further investigations are necessary to determine the specific aspects of NCC that contribute to these improved outcomes and its cost-effectiveness.