Older people are frequent emergency department (ED) users who present with complex issues that are linked to poorer health outcomes following the index visit, often have increased ED length of stay, and tend to have raised healthcare costs. Encouraging evidence suggests that ED teams involving health and social care professionals (HSCPs) can contribute to enhanced patient flow and an improved patient experience by improving care decision-making and thus promoting timely and effective care. However, the evidence supporting the impact of HSCP teams assessing and intervening with older adults in the ED is limited and identifies important methodological limitations, highlighting the need for more robust and comprehensive investigations of this model of care. This study aims to evaluate the impact of a dedicated ED-based HSCP team on the quality, safety, and clinical- and cost-effectiveness of care of older adults when compared with usual care.The study is a single-site randomised controlled trial whereby patients aged ≥65 years who present to the ED of a large Irish hospital will be randomised to the experimental group (ED-based HSCP assessment and intervention) or the control group (usual ED care). The recruitment target is 320 participants. The HSCP team will provide a comprehensive functional assessment as well as interventions to promote a safe discharge for the patient. The primary outcome is ED length of stay (from arrival to discharge). Secondary outcomes include: rates of hospital admissions from the ED, ED re-visits, unplanned hospital admissions and healthcare utilisation at 30 days, and 4 and 6 months of follow-up; patient functional status and quality of life (at baseline and follow-up); patient satisfaction; cost-effectiveness in terms of costs associated with ED-based HSCP compared with usual care; and perceptions on implementation by ED staff members.This is the first randomised controlled trial testing the impact of HSCPs working in teams in the ED on the quality, safety, and clinical- and cost-effectiveness of care for older patients. The findings of this study will provide important information on the effectiveness of this model of care for future implementation.ClinicalTrials.gov, NCT03739515 . Registered on 12 November 2018.