Fetal alcohol spectrum disorder (FASD) is prevalent among individuals involved in the justice system. However, many of the characteristics of justice-involved individuals with FASD remain unknown. We assessed patients in a forensic mental health hospital (n = 26) for FASD before their release. The two objectives were to establish the prevalence of FASD in this unique environment and to describe the mental health and neurocognitive characteristics of individuals with FASD compared to patients with complex needs and those without FASD. The prevalence of FASD was 46%. We found the FASD group to have more than six impaired brain domains, greater than the other groups, and a higher prevalence of ADHD.