PROJECT SUMMARY/ABSTRACT People with serious mental illnesses (SMI) are disproportionately represented throughout the criminal justice system, the vast majority of whom are on probation and parole. Implementing evidence-based practices to address the needs of justice-involved people with SMI requires an understanding of the multilevel factors that impact intervention implementation in both the mental health and criminal justice systems and the expertise to address these factors. Dr. Tonya Van Deinse’s proposed K01 training plan and research study, under the expert guidance of an NIH-funded mentoring team, will provide her with intensive substantive and methodological training and research experience to become a leading expert in implementing complex, cross- agency interventions to address the needs of justice-involved people with SMI. Specialty mental health probation (SMHP) is an evidence-informed intervention that aims to engage people with SMI in treatment and divert them from the criminal justice system. Although high-fidelity SMHP can increase mental health and substance use service engagement, improve mental health symptoms, and reduce rates of rearrest, jail days and probation violations, effective implementation of SMHP is context-dependent and relies on inter- organizational relationships between SMHP officers and mental health service providers. Specifically, SMHP requires officers to increase treatment linkage and resource coordination and serve as boundary spanners who bridge the interagency coordination and collaboration gap between probation officers and mental health service providers. Given the importance of inter-organizational relationships in implementing SMHP, it is necessary to assess the multilevel factors that impact its cross-agency implementation context and to develop implementation strategies to enhance inter-organizational relationships. This proposal adapts an existing implementation approach to enhance probation officers’ capacity for coordination, collaboration, and linking probationers with SMI to treatment. This adapted implementation approach, to be called Networking to Engage in Treatment: Working within Officer-Resource Collaboratives (NETWORC), will be developed and tested via the following aims: (1) identify multi-level factors that inhibit SMHP officers’ capacity to link individuals with SMI to treatment providers; (2) conduct a process evaluation of the NETWORC implementation approach; and (3) evaluate the efficacy, acceptability, appropriateness, and feasibility of the collaborative implementation toolkit. Findings from this study will provide preliminary data about the feasibility and efficacy of the adapted implementation strategy and will be used to develop Dr. Van Deinse’s subsequent R01, a pragmatic cluster randomized trial using multilevel analyses to examine the impact of the implementation strategy on probationer, officer, and inter-organizational levels.