Forgiveness interventions are a promising approach to conflict resolution, anger-reduction and the enhancement of emotional well-being in adults. The present study examined the effectiveness of a novel six-session, problem-oriented forgiveness group intervention for Greek preadolescents. The sample consisted of 42 primary school students aged 10-13 years, allocated to the experimental (n = 21) or control group (n = 21). The intervention was evaluated using both quantitative and qualitative methods. Results indicated that, compared to the control group, participants in the experimental group showed a significant reduction in feelings of depression and anger as well as an increase in satisfaction with life. In addition, experimental group participants showed a better understanding of forgiveness and developed a more positive attitude towards their offenders. A 12-month follow-up further supported the long-term impact of the forgiveness intervention. Practical implications for the design and implementation of universal forgiveness programmes for older children are discussed.