As many as two-thirds of Justice-involved Veterans (JIVs) have a substance-use disorder (SUD), and up to 51% have a mental health (MH) condition; however, fewer than one-third of JIVs receive MH or SUD treatment, and addressing stigma is a recommended strategy for improving Veteran willingness to engage in treatment. Honest, Open, Proud (HOP) is an evidence-based stigma reduction intervention for justice-involved Veterans that is delivered by peers, which can ultimately increase access to and engagement in care, lower rates of criminal recidivism, and improve MH and SUD outcomes. However, implementation of such interventions with high-acuity patients often requires strategies that are intensive and costly. This trial will evaluate the relative impacts and costs of using a high-intensity (vs. low-intensity) strategy to implement a peer-led, stigma reduction intervention for justice-involved Veterans with co-occurring SUD and MH disorders.