The purpose of the present paper was to review the current models of mental health service delivery used in the emergency department (ED) setting. A search was conducted of the nursing and medical literature from 1990 to 2007 for relevant articles and reports. Consideration was also given to the global and local context influencing contemporary mental health services. Wider sociopolitical and socioeconomic influences and systemic changes in health-care delivery have dictated a considerable shift in attention for mental health services worldwide. The ED is a topical location that has attracted interest and necessitated a response. The mental health liaison nurse (MHLN) role embedded within the ED structure has demonstrated the most positive outcomes to date. This model aims to raise mental health awareness and address concerns over patient-focused outcomes such as reduced waiting times, therapeutic intervention and more efficient coordination of care and follow up for individuals presenting to the ED in psychological distress. Further research is required into all methods of mental health service delivery to the ED. The MHLN role is a cost-effective approach that has gained widespread approval from ED staff and mental health patients and is consistent with national and international expectations for mental health services to become fully integrated within general health care. The mental health nurse practitioner role situated within the ED represents a potentially promising alternative for enhanced public access to specialized mental health care.