Reminiscence-based interventions focus on the recall of autobiographical memories and reflective reasoning about these remembered experiences. This study assessed the effect of a three-session, positive-memory version of cognitive-reminiscence therapy (CRT) on the psychological resources and mental well-being of young adults. The participants (N=62, Mage=24.6 [SD=3.1], 71% females) were randomised to CRT or wait-list. Psychological resources (self-esteem, self-efficacy, meaning in life, optimism), mental well-being (depression, anxiety, and stress symptoms) and theorised change processes (automatic negative thoughts, awareness of narrative identity and cognitive reappraisal) were assessed. The results showed the CRT group was significantly higher on psychological resources at post-CRT (d=0.75-0.80) and follow-up (d=0.52-0.87), and mental well-being at post-intervention (d=0.71–1.30) and follow-up (d=0.64–0.98). The hypotheses regarding change processes were supported. Future research may use an active comparator and longer follow-ups. Brief, positive-focused CRT is effective in increasing psychological resources and mental well-being in young adults.