The purpose of this paper is to review current national and international perspectives on the role and function of mental health nursing in dual disability within acute mental health inpatient settings. A universally accepted definition of the role and function of psychiatric nursing has been elusive. The role and function may be presumed to have core attributes that differ according to local conditions. The articulation of the role and function will contribute to the body of knowledge of psychiatric nursing and to improving the understanding of the nurse-patient relationship for those caring for people with dual disability in acute mental health inpatient facilities. The two identified key roles and functions of mental health nursing practice for people with intellectually disabilities within acute inpatient mental health facilities in Victoria will be discussed.