The primary aim of this study was to screen for mental health problems in Australian Indigenous young people in a youth detention centre using the Westerman Aboriginal Symptoms Checklist – Youth (WASC-Y). Over the study period, all Indigenous young people admitted into custody were referred for screening with the WASC-Y, a culturally validated fivescaled instrument developed to identify Indigenous young people at risk for a range of mental health or substance abuse problems. The WASC-Y also incorporates a separate scale for cultural resilience. High levels of mental health and substance abuse problems were reported, with 94.6% of males and 100% of females surveyed screening above the designated clinical cut-off on at least one scale. Based on moderate/medium levels of risk, 27.7% screened positive for depression, 34.0% for suicide ideation or intent, 89.4% for substance use, 36.2% for impulsivity, and 68.1% for symptoms of anxiety. Females screened higher than males across all five subscales, though differences reached statistical significance only for suicidal ideation or intent. Cultural resilience as a protective factor for mental health problems (excluding substance abuse) approached clinical significance. Given their pervasively high levels of psychological distress, it is recommended that on admission into custody all Indigenous youth are referred for a mental health assessment and substance abuse counselling. It is important to assess for culturally resiliency or other strengths that may be protective against mental health problems.