This study sought to identify the incidence of mental illness, substance misuse, and cognitive impairment among a representative cohort of 123 Aboriginal people in custody in Australia. In addition, the study measured levels of social and emotional well-being (SEWB) and considered the interrelationship of mental health issues, SEWB, and unmet needs. Both male and female Aboriginal prisoners were found to have high rates of mental health, substance abuse, and cognitive functioning needs that were heavily contextualized within perceptions of their own SEWB. Findings provide important information with regard to the specific needs of Aboriginal people in custody. Implications for the development and implementation of effective, culturally themed best practice programming for this population are discussed.