BACKGROUND: Ethnic minority groups are under-represented in mental health care services because of barriers such as poor mental health literacy. In 2007, the Mental Health First Aid (MHFA) program implemented a cultural adaptation of its first aid course to improve the capacity of Indigenous Australians to recognise and respond to mental health issues within their own communities. It became apparent that the content of this training would be improved by the development of best practice guidelines. This research aimed to develop culturally appropriate guidelines for providing first aid to an Australian Aboriginal or Torres Strait Islander person who is experiencing a mental health crisis or developing a mental illness. METHODS: A panel of Australian Aboriginal people who are experts in Aboriginal mental health, participated in six independent Delphi studies investigating depression, psychosis, suicidal thoughts and behaviours, deliberate self-injury, trauma and loss, and cultural considerations. The panel varied in size across the studies, from 2024 participants. Panellists were presented with statements about possible first aid actions via online questionnaires and were encouraged to suggest additional actions not covered by the survey content. Statements were accepted for inclusion in a guideline if they were endorsed by > or = 90% of panellists as essential or important. Each study developed one guideline from the outcomes of three Delphi questionnaire rounds. At the end of the six Delphi studies, participants were asked to give feedback on the value of the project and their participation experience. RESULTS: From a total of 1,016 statements shown to the panel of experts, 536 statements were endorsed (94 for depression, 151 for psychosis, 52 for suicidal thoughts and behaviours, 53 for deliberate self-injury, 155 for trauma and loss, and 31 for cultural considerations). The methodology and the guidelines themselves were found to be useful and appropriate by the panellists. CONCLUSION: Aboriginal mental health experts were able to reach consensus about culturally appropriate first aid for mental illness. The Delphi consensus method could be useful more generally for consulting Indigenous peoples about culturally appropriate best practice in mental health services.