The study aimed to assess the psychometric properties of the Indigenous Risk Impact Screen (IRIS) as a screening instrument for determining (i) the presence of alcohol and drug and mental health risk in Indigenous adult Australians and (ii) the cut-off scores that discriminate most effectively between the presence and absence of risk. A cross-sectional survey was used in clinical and non-clinical Indigenous and non-Indigenous services across Queensland Australia. A total of 175 Aboriginal and Torres Strait Islander people from urban, rural, regional and remote locations in Queensland took part in the study. Measures included the Indigenous Risk Impact Screen (IRIS), the Severity of Dependence Scale (SDS), the Alcohol Use Disorders Identification Test (AUDIT) and the Leeds Dependence Questionnaire (LDQ). Additional Mental Health measures included the Depression Anxiety and Stress Scale (DASS-21) and the Self-Report Questionnaire (SRQ). Principle axis factoring analysis of the IRIS revealed two factors corresponding with (i) alcohol and drug and (ii) mental health. The IRIS alcohol and drug and mental health subscales demonstrated good convergent validity with other well-established screening instruments and both subscales showed high internal consistency. A receiver operating characteristics (ROC) curve analysis was used to generate cut-offs for the two subscales and t-tests validated the utility of these cut-offs for determining risky levels of drinking. The study validated statistically the utility of the IRIS as a screen for alcohol and drug and mental health risk. The instrument is therefore recommended as a brief screening instrument for Aboriginal and Torres Strait Islander people.