Study objective: Older adults presenting to the emergency department (ED) are at high risk of adverse health outcomes. This study aimed to evaluate the accuracy of 4 frequently used screening instruments for the prediction of adverse health outcomes among older adults in the ED. Methods: This was a prospective cohort study in patients ≥70 years of age presenting to the ED in 2 hospitals in the Netherlands. Screening instruments included the acutely presenting older patient screening program (APOP) (providing 2 risk scores—functional decline [APOP1] and mortality [APOP2]), the International Resident Assessment Instrument Emergendy Department screener (InterRAI ED), the Identification of Seniors At Risk-Hospitalized Patients (ISAR-HP), and the safety management system (VMS). The primary outcome measure was a composite outcome encompassing functional decline, institutionalization, and mortality at 3 months after ED presentation. Other follow-up time points were 1 and 6 months. Analyses were performed to assess prognostic accuracy. Results: In total, 889 patients were included. After 3 months, 267 (31%) patients experienced at least 1 adverse outcome. The positive likelihood ratio ranged from 1.67 (VMS) to 3.33 (APOP1), and the negative likelihood ratio ranged from 0.41 (ISAR-HP) to 0.88 (APOP2). Sensitivity ranged from 17% (APOP2) to 74% (ISAR-HP), and specificity ranged from 63% (ISAR-HP) to 94% (APOP2). The area under the curve ranged from 0.62 (APOP2) to 0.72 (APOP1 and ISAR-HP). Calibration was reasonable for APOP1 and VMS. The prognostic accuracy was comparable across all outcomes and at all follow-up time points. Conclusion: The frailty screening instruments assessed in this study showed poor to moderate prognostic accuracy, which brings into question their usability in the prediction of adverse health outcomes among older adults who present to the ED.