Older adults represent a growing proportion of ED visits and are disproportionately vulnerable to adverse outcomes due to higher rates of frailty, multimorbidity, and physiologic decline. Given the risk of adverse outcomes, frailty and vulnerability screening tools have been proposed as a way to rapidly identify high-risk older patients and allocate resources more efficiently; however, this systematic review demonstrates that most frailty and vulnerability tools offer high sensitivity but poor specificity, limiting their ability to meaningfully predict clinical deterioration. As a result, these tools may function better for ruling out low-risk patients rather than for identifying those who require intensive monitoring or intervention. Notably, the review highlights a critical evidence gap: despite widespread clinical enthusiasm, current tools do not provide sufficient prognostic accuracy to replace clinician judgement or guide ED treatment plans. Continued research is needed to refine such screening instruments along with validating them across diverse ED settings. With further research, these tools could potentially show an ability to improve patient-centered outcomes, resource utilization, or care pathways for older adults.