BackgroundIt is estimated that the prevalence of mental illness is higher in Aboriginal and Torres Strait Islander adolescents compared to non-Aboriginal adolescents. Despite this, only a small proportion of Aboriginal youth have contact with mental health services, possibly due to factors such as remoteness, language barriers, affordability and cultural sensitivity issues. This research aimed to develop culturally appropriate guidelines for anyone who is providing first aid to an Australian Aboriginal or Torres Strait Islander adolescent who is experiencing a mental health crisis or developing a mental illness.MethodsA panel of Australian Aboriginal people who are experts in Aboriginal youth mental health, participated in a Delphi study investigating how members of the public can be culturally appropriate when helping an Aboriginal or Torres Strait Islander adolescent with mental health problems. The panel varied in size across the three sequential rounds, from 37–41 participants. Panellists were presented with statements about cultural considerations and communication strategies via online questionnaires and were encouraged to suggest additional content. All statements endorsed as either Essential or Important by ≥ 90% of panel members were written into a guideline document. To assess the panel members’ satisfaction with the research method, participants were invited to provide their feedback after the final survey.ResultsFrom a total of 304 statements shown to the panel of experts, 194 statements were endorsed. The methodology was found to be useful and appropriate by the panellists.ConclusionAboriginal and Torres Strait Islander Youth mental health experts were able to reach consensus about what the appropriate communication strategies for providing mental health first aid to an Aboriginal and Torres Strait Islander adolescent. These outcomes will help ensure that the community provides the best possible support to Aboriginal adolescents who are developing mental illnesses or are in a mental health crisis.