Background: Among the 146,000 Veterans released from correctional settings annually, approximately 60% have a co-occurring mental health and substance use disorder (COD). These individuals often access treatment inconsistently, resulting in increased antisocial activities and acceleration into unemployment and homelessness – strong predictors of reoffending. VHA Mental Health Residential Rehabilitation Treatment Programs (MH RRTPs) commonly serve justice-involved Veterans (JIVs) with an estimated 50% annually. JIVs receive assistance with their addiction and behavioral health needs, but MH RRTP programs do not directly address their antisocial behaviors and cognitions. Furthermore, MH RRTP discharge is a vulnerable transition and no national transitional approach facilitates Veteran engagement in prosocial community behaviors that maintain MH RRTP gains, and ultimately reducing revolving door service use. Maintaining Independence and Sobriety through Systems Integration, Outreach, and Networking-Criminal Justice version (MISSION-CJ) is a new case manager and peer delivered team-based treatment for JIVs with a COD. Three recent open pilots of MISSION-CJ showed reduced criminal recidivism, improved behavioral health outcomes and increased access and engagement in care. A randomized controlled trial (RCT) is a critical next step prior to dissemination. Significance/Impact: This application is responsive to the VHA MISSION Act, Veteran Care Priorities of Access to Care, Mental Health, and Health Equity. The project aims to (a) increase access and engagement in VHA and community-based care, (b) offer timely Veteran-centered care, and (c) improve the health and well- being of JIVs while reducing disparities. It also includes an implementation aim to support VHA learning. Innovation: While MISSION-CJ derives in part from an evidence-based treatment for homeless individuals (MISSION), it includes a new conceptual framework and numerous new and differentiating features for a CJ population including: (1) a treatment planning tool focused on criminogenic needs that monitors progress and tunes service delivery elements, (2) a prosocial treatment curriculum, and (3) tools/resources to address Veteran legal issues. With MISSION-CJ, this study attempts to change the practice paradigm and transform care for JIVs by moving beyond the current model of linking Veterans to VA care and tracking behavioral health outcomes, to a hybrid treatment/linkage approach that addresses criminogenic needs, supports engagement in VA and non-VA care, and targets recidivism as an outcome–the gold standard for CJ research. Specific Aims: Aim 1: An RCT will compare MISSION-CJ to EUC. We predict that those in MISSION-CJ will have (1a) lower criminal recidivism; (1b) lower overall risk for criminal recidivism; (1c) better health-related outcomes (substance use, mental health, housing, employment); and (1d) the effects of MISSION-CJ on 1a, 1b and 1c, will be mediated by (i) reductions a...