The increasing proportion of older adults presenting to emergency departments (EDs) has created significant challenges for healthcare systems worldwide. Older patients frequently present with complex multimorbidity, functional impairment, cognitive decline, and increased vulnerability to acute stressors. Frailty, defined as a state of decreased physiological reserve and increased susceptibility to adverse health outcomes, has emerged as an important predictor of hospitalization, mortality, and functional deterioration. Emergency department-based frailty assessment tools may provide rapid identification of high-risk older adults and support individualized clinical decision-making. This systematic review and meta-analysis aimed to evaluate the predictive performance of frailty assessment instruments applied in emergency departments for hospitalization, mortality, and other adverse outcomes among older adults. A comprehensive literature search performed in major biomedical databases to identify studies evaluating validated frailty assessment tools in ED populations aged ≥65 years. Eligible studies assessed the association between frailty measurements and clinical outcomes, including hospital admission, short- and long-term mortality, intensive care utilization, functional decline, and adverse events. Data regarding study characteristics, frailty instruments, predictive performance measures, and outcomes extracted and synthesized. The pooled evidence demonstrated that ED-based frailty assessment tools were significantly associated with increased risk of hospitalization and mortality. Instruments including the Clinical Frailty Scale (CFS), Identification of Seniors at Risk (ISAR), Emergency Department Frailty Index (ED-FI), and Frailty Phenotype demonstrated moderate-to-high predictive accuracy. Frailty assessment improved risk stratification beyond chronological age alone and provided clinically meaningful information regarding patient vulnerability. However, heterogeneity existed regarding assessment methods, outcome definitions, and follow-up periods. Frailty screening in emergency departments represents a valuable approach for identifying older adults at increased risk of adverse outcomes. Integration of rapid frailty assessment into routine emergency care may improve triage decisions, facilitate appropriate resource allocation, and support patient-centered management strategies.