Mental health triage/duty services play a pivotal role in the current framework for mental health service delivery in Victoria and other states of Australia. Australia is not alone in its increasing reliance on mental health triage as a model of psychiatric service provision; at a global level, there appears to be an emerging trend to utilize mental health triage services staffed by nurses as a cost-effective means of providing mental health care to large populations. At present, nurses comprise the greater proportion of the mental health triage workforce in Victoria and, as such, are performing the majority of point-of-entry mental health assessment across the state. Although mental health triage/duty services have been operational for nearly a decade in some regional healthcare sectors of Victoria, there is little local or international research on the topic, and therefore a paucity of established theory to inform and guide mental health triage practice and professional development. The discussion in this paper draws on the findings and recommendations of PhD research into mental health triage nursing in Victoria, to raise discussion on the need to develop theoretical models to inform and guide nursing practice. The paper concludes by presenting a provisional model for mental health triage nursing practice.