Indigenous Australians have high rates of mental illness comorbid with substance misuse. The complex needs of this client group create challenges for the alcohol and other drug (AOD) workforce. This paper describes the outcomes of an Indigenous-specific “Yarning about Mental Health” training for the AOD workforce to strengthen knowledge and skills in mental health approaches and in their engagement with Indigenous clients. The training provides culturally adapted strategies and tools for understanding mental health, promoting wellbeing, and delivering brief interventions in the substance misuse setting. A nonexperimental evaluation which incorporated pre-post questionnaires was conducted with workshop participants attending one of four trainings. The training was perceived to be highly appropriate and helpful in participants’ work with Indigenous AOD clients. There was significant improvement in confidence and knowledge related to Indigenous mental health and wellbeing and qualitative data supported these positive outcomes. This study supports the need to blend Indigenous concepts of health and wellbeing with non-Indigenous ways of understanding and treating illness in order to develop services which are appropriate to Indigenous peoples. It also suggests research is required to understand whether self-reported increases in knowledge and confidence can translate into behavioural changes in participants' teaching and practice of culturally competent care and to improved client outcomes.