Study objective We evaluate the diagnostic test characteristics of the Six-Item Screener and the AD8 to detect cognitive dysfunction in adults older than 65 years and using the emergency department (ED) for any reason. Methods We conducted an observational cross-sectional cohort study at a single academic urban university-affiliated hospital. Subjects were consenting, noncritically ill, English-speaking adults older than 65 years and receiving care in the ED. We quantitatively assessed the diagnostic test characteristics of the Six-Item Screener and AD8 by using the Mini-Mental State Examination score less than 24 as the criterion standard for cognitive dysfunction. Results The prevalence of cognitive dysfunction was 35%, but only 6% of charts noted a pre-existing deficit. The Six-Item Screener was superior to either the caregiver-administered AD8 or the patient-administered AD8 for the detection of cognitive dysfunction. Conclusion The Six-Item Screener was superior to the caregiver- or patient-administered AD8 to identify older adults at increased risk for occult cognitive dysfunction.