Background: Cognitive impairment is highly prevalent among older patients attending the Emergency Department (ED) and is associated with adverse outcomes. Methods: we conducted a systematic review and meta-analysis to evaluate the diagnostic accuracy of cognitive screening instruments to rule out cognitive impairment in older patients in the ED. A comprehensive literature search was performed in MEDLINE, EMBASE, CINAHL and CENTRAL. A risk of bias assessment using QUADAS-2 was performed. Results: 23 articles, examining 18 different index tests were included. Only seven index tests could be included in the meta-analysis. For ruling out cognitive impairment irrespective of aetiology, Ottawa 3 Day Year (O3DY) (pooled sensitivity 0.90; (95% CI) 0.71-0.97) had the highest sensitivity. Fourteen articles focused on screening for cognitive impairment specifically caused by delirium. For ruling out delirium, the 4 A's Test (4AT) showed highest sensitivity (pooled sensitivity 0.87, 95% confidence interval (95% CI) 0.74-0.94). Conclusions: High clinical and methodological heterogeneity was found between included studies. Therefore, it is a challenge to recommend one diagnostic test for use as a screening instrument for cognitive impairment in the ED. The 4AT and O3DY seem most promising for ruling out cognitive impairment in older patients attending the ED. The review protocol was registered in PROSPERO (CRD42018082509).