Prisoners display significantly higher rates of mental disorders and lower mental wellbeing than the general population. The integration of positive psychological interventions in offender supervision has received recent advocacy. The aim of the current pre-post pilot study was to determine the short-term effects of group-based resilience training on mental health outcomes for female offenders and explore intervention acceptability. Offenders (n = 24) self-selected to partake in a multi-component psychological skill program based on positive psychology, cognitive–behavioural therapy, and mindfulness-based activities. The training was taught in nine sessions of 1.5 hr each. Baseline and follow-up measurements of mental wellbeing and psychological distress were collected and focus groups conducted to investigate participants’ experiences, acceptability, and appropriateness of the training. Moderate to large effect sizes indicating significant improvements were observed for wellbeing, g = 0.75 and distress, g = 0.56. Training was well received by participants and staff and was delivered feasibly within the prison context. The results are encouraging, and a future well-powered study using a rigorous controlled design is warranted.