Recent recommendations from the Society for Academic Emergency Medicine and the American College of Emergency Physicians identified the detection of delirium in the emergency department (ED) as a ‘high yield’ research objective. This review aimed to determine the occurrence rate, and physician detection rates, of delirium within the ED. A systematic literature review was conducted and identified using online databases. Prospective cohort and cross-sectional studies from hospital EDs were interrogated. Systematic data extraction and assessments of quality were carried out. Searching yielded 723 publications, and 13 papers met inclusion criteria. Occurrence of delirium at admission to the ED ranged from 7% to 20% of patients. Physician diagnosis rates of preconfirmed delirium (using a specified tool) within the ED varied between 11.1% and 46.0%. Many studies used non-validated assessment tools to gather data. Four delirium outcome studies were conducted in the ED setting. Results vary, with several being of poor quality; however, delirium at ED presentation may have a significant effect on long-term outcomes. Delirium is a significant concern in the ED, with many delirious patients not identified by physicians. Given the scale, addressing delirium should be a priority for clinicians and researchers. To improve delirium outcomes and hospital management, measures must include mechanisms to improve detection. Finding a single validated assessment method and facilitating research in this difficult patient population would be an important progress.