This study pilot-tested a values and mindfulness-based intervention (Re-Entry Values and Mindfulness Program: REVAMP) in a sample of male jail inmates. REVAMP aimed to reduce post-release risky behavior by targeting dimensions of mindfulness (e.g., willingness/acceptance) and associated proximal outcomes/ mechanisms of action (emotion regulation, self-control, shame/guilt). Inmates were randomly assigned to REVAMP (n = 21) or treatment as usual (TAU, n = 19). Attendance and feedback supported REVAMP’s feasibility and acceptability. At post-treatment, ANCOVAs showed that the REVAMP group increased more on willingness/acceptance, self-judgment, and shame relative to TAU. Relative increases in willingness/acceptance persisted at 3-month post-release. Criminal activity was assessed by self-report at 3 months post-release and official criminal records at 3 years post-release. At both time points, there was a marginally statistically significant trend of medium effect size for lower criminal recidivism in the REVAMP group compared to TAU. There were no statistically significant differences in self-reported post-release substance misuse. This pilot RCT indicated mindfulness-based interventions may hold promise for reducing inmates’ post-release risky behavior and encourages future research in this area.