Despite substantial efforts to curb Veteran suicide, Veterans continue to die by suicide at rates that far exceed their civilian peers. To date, substantial resources have been invested into understanding and treating underlying risk factors and precipitants of Veteran suicide. However, criminal justice involvement remains an under-examined and under-assessed risk factor for Veteran suicide. Accumulating research suggests justice-involved Veterans are a high-risk, high- need population, particularly within the Veterans Health Administration. For example, 11% of Veteran suicides are precipitated by legal troubles; 79% of Veterans receiving VA supportive housing assistance have a history of one or more arrests; and 58% of Veterans receiving outpatient VHA substance use treatment have a history of three or more arrests. Risk for suicide among justice-involved Veterans is particularly elevated among those with co-occurring difficulties, such as mental health concerns and/or housing instability. Adequately addressing Veteran suicide – both for justice-involved Veterans and the broader Veteran population – therefore likely requires interventions to address the legal and co-occurring difficulties of at-risk Veterans. Dialectical Behavior Therapy for Justice-Involved Veterans (DBT-J) is distinctively designed to address these range of needs faced by justice-involved Veterans, including heightened suicide risk, antisocial behaviors, mental health and substance use concerns, community-based structural barriers, and case management difficulties. Combining elements of three prominent, evidence-based models, DBT-J provides 16 weeks of group psychotherapy, case management services, and measurement-based care to Veterans with ongoing or recent criminal justice involvement. Data from two prior clinical trials completed by the proposed study’s Principal Investigator attest to the feasibility and acceptability of DBT-J within VHA behavioral health settings. Although preliminary, data also suggest participation in DBT-J may yield meaningful reductions in risk for future criminal behavior and resolution of high-priority case management needs. Continued research, however, is needed to further investigate the program’s efficacy. Toward these aims, the proposed Phase III clinical trial will: 1) Primary Aims 1-2: Assess the superiority of DBT-J over supportive group therapy in decreasing risk of future criminal behavior and increasing psychosocial functioning. 2) Secondary Aim: Assess the superiority of DBT-J over supportive group therapy in improving secondary treatment targets (i.e., suicidal ideation, criminogenic thinking, psychological distress, substance use, case management needs, quality of life, resilience, suicide-related behavior, and criminal recidivism). 3) Exploratory Aims 1-2: Assess for differential efficacy of DBT-J across high-priority JIV subgroups (i.e., violent versus nonviolent most recent offense type, presence/absence of a substance use d...