Abstract Rationale: Critical illness in patients living with frailty has been reported to be associated with poor health outcomes. Understanding its impact on key outcomes such as mortality, and function is crucial for guiding care strategies and informed shared decision-making in this vulnerable population. This systematic review and meta-analysis provides an updated synthesis of evidence evaluating mortality and likelihood of discharge home in frail patients with critical illness. Methods: We registered this review on Prospero (CRD42023473646) and ensured it follows Meta-analysis of Observational Studies in Epidemiology (MOOSE) and PRISMA guidelines. We searched MEDLINE, EMBASE, CINAHL, ClinicalTrials.gov, and the Cochrane Library up to October 23, 2023, and included observational studies and randomized controlled trials reporting outcomes of adult, critically ill, frail populations. We included studies in all types of ICUs that used a validated frailty ascertainment tool. Two reviewers independently conducted study selection and data extraction. Using RevMan, we conducted random-effects meta-analysis to determine the association of frailty with long-term mortality (≥ 3 months), hospital mortality, and discharge home. We report Risk Ratios (RR) and 95% Confidence Intervals (CIs). We conducted subgroup analyses examining various frailty instruments and ICU type [Medical-Surgical ICU (MSICU) or Cardiovascular ICU (CVICU)]. Results: From 4,687 citations, we included 90 studies with 92 reports and 102 analyses. Frail patients had higher hospital mortality RR 2.29 (95% CI 1.95-2.70), long-term mortality RR 2.59 (95% CI 2.26-2.97) (Figure 1) and were less likely to be discharged home RR 0.43 (95% CI 0.39-0.47) compared with non-frail patients. Subgroup analysis revealed frailty was linked to increased long-term mortality in MSICUs RR 1.75 (95% CI 1.60-1.92) and CVICUs RR 1.68 (95% CI 0.79-3.57). The RR for long-term mortality for frailty across instruments was; Clinical Frailty Scale 1.86 (95% CI 1.61-2.09), Edmonton Frail Scale 2.44 (95% CI 1.67-3.57), Frailty Index 1.40 (95% CI 1.23-1.58), Frailty Phenotype 2.56 (95% CI 1.22-5.37), Hospital Frailty Risk Score 1.72 (95% CI 1.53-1.94), Modified Frailty Index-5 0.84 (95% CI 0.55-1.27) and Modified Frailty Index-11 1.70 (95% CI 1.48-1.95). Conclusions: Frailty is associated with adverse outcomes in critically ill patients. The strength of the association varies by type and frailty ascertainment tool. These findings underscore the importance of standardizing frailty assessment and the need to investigate targeted interventions to improve outcomes in frail critically ill patients. Funding: The Canadian Frailty Network