ABSTRACT: This paper describes the establishment of a mental health nurse practitioner (MHNP) position in New South Wales, Australia. The authors report on a MHNP role that functions collaboratively within a large inner city emergency department. Attention is centred on what constitutes advanced mental health nursing practice in the emergency department setting. Three areas associated with the work of MHNPs – therapeutic techniques, prescribing and care coordination and referral – are highlighted to explore the scope of the MHNP role. The authors propose that the success of this position is based on a process of consultation and evaluation, partnership between disciplines and clinical services and the role maintaining a truly nursing focus rather than attempting to replace or replicate psychiatric medicine.