Background: The practice environment of the emergency department (ED) refers to both the people and physical factors (architecture) in the environment in which health care is provided. ED triage practice environments are the very places where caring or the delivery of health care often begins. This paper examines the implications of the emergency department triage practice environment on the triage practice of nurses who triage clients with a mental illness. Methods: An observational ethnographic approach inclusive of participant observation, formal and informal semi structured interviews, examination of documents and the collation of field notes were the means of data collection. Data was analysed through constant comparison and theoretical coding. Results: Nurses who work in ED triage are cognisant of environmental impacts as they undertake rapid client assessment and manage busy and noisy waiting rooms. The triage environment does influence the ED triage assessment and the management of clients who present seeking mental health care.