The Brooklyn Mental Health Court (BMHC) seeks to address the overrepresentation of individuals with mental illness in the criminal legal system while maintaining public safety. This is accomplished through a combination of treatment—providing participants with the supports they need—and judicial supervision. Prior research has suggested that mental health court participation, and especially successful completion, reduces future system contact. This study expands our understanding of the model by identifying specific in-program events and other factors that contribute to unsuccessful program outcomes. Specifically, we found that those admitted to the program on violent felony charges and/or with co-occurring neurodevelopmental disorders were no more (or less) likely to complete the program than other participants. In contrast, several in-program events (new arrests, absconding from treatment, posing a threat to others, psychiatric competency exam ordered) all contribute to unsuccessful program outcomes. Asked about the program overall and a recent BJA-funded expansion, stakeholders noted several program strengths and widely appreciated that the program enhancements allowed them to reach more participants. However, they also reported that limited resources in the community are a major challenge in supporting court-involved individuals with serious and persistent mental illness.