Abstract: This paper reports the three-stage development of a professional practice audit questionnaire for mental health nursing in Aotearoa/New Zealand. In Study 1, clinical indicator statements (n = 99) generated from focus group data, which were considered to be unobservable in the nursing documentation in consumer case notes, were included in a three-round Delphi process. Consensus of ratings occurred for the mental health nurse and academic participants (n = 7) on 83 clinical indicator statements. In Study 2, the clinical indicator statements (n = 67) that met importance and consensus criteria were incorporated into a questionnaire, which was piloted at a New Zealand mental health service. The questionnaire was then modified for use in a national field study. In Study 3, the national field study, registered mental health nurses (n = 422) from 11 New Zealand district health board mental health services completed the questionnaire. Five categories of nursing practice were identified: professional and evidence-based practice; consumer focus and reflective practice; professional development and integration; ethically and legally safe practice; and culturally safe practice. Analyses revealed little difference in the perceptions of nurses from different backgrounds regarding the regularity of the nursing practices. Further research is needed to calibrate the scores on each clinical indicator statement with behaviour in clinical practice.