A quasi-experimental pre-test/post-test study was carried out to investigate the effects of the EQUIP programme on moral judgement, social skills, cognitive distortions and social information processing of juvenile delinquents. The programme is designed to equip antisocial youth to think and act responsibly, and is a combination of Positive Peer Culture (PPC) and the teaching of helping skills. Participants were recruited from three comparable high-security correctional facilities for convicted boys between the ages of 12 and 18 years. One of these facilities implemented the EQUIP programme ( n =31); the other two facilities provided the control group ( n =25). Analysis of covariance on the post-test scores with the pre-test scores as the covariate showed a greater reduction of cognitive distortions in general for the EQUIP group when compared with the control group. No differences were found on moral judgement, social skills and social information processing. However, a few aspects of social information processing showed modest effect sizes in favour of the experimental group. It is concluded that to strengthen the effects of EQUIP a more intensive treatment is recommended. Future research on EQUIP should include more participants and investigate the impact of the programme on different types of antisocial youths.