Nurture groups (NGs) are an intervention implemented to improve the social, emotional and behavioural functioning of vulnerable children and they are increasingly being used within secondary school settings (Colley 2009). The psychological processes underpinning change within a NG intervention for adolescents has been identified as a topic that warrants further research (Garner and Thomas 2011). This study aimed to explore the processes involved in promoting change in participants of secondary school NGs through evidence provided by questionnaires and through a thematic analysis of NG practitioners' perspectives. Participants were identified through SDQ screening and teacher referral; there were 29 male and 20 female young people aged between 11 and 14 years in part-time NGs for two terms. In addition, nine NG practitioners took part in semi-structured individual interviews. This study used questionnaires completed pre- and post-intervention by young people, parents/carers and teachers to explore changes in observed attachment-related behaviours and social, emotional and behavioural functioning in young people following NG participation. In addition, a thematic analysis was completed to explore NG practitioners' perspectives on change and secondary school NG processes. The measures were the Boxall Profile for Young People, the Strengths and Difficulties Questionnaire and the Social Skills Questionnaire. The results showed that parent, teacher and young person emotional symptoms scores and total difficulties scores reduced following NG participation. No significant changes in social skills levels or attachment-related behaviours were seen. From a thematic analysis of interviews with NG practitioners, themes of change and mechanisms of change emerged. Findings are discussed in terms of attachment theory and social learning theory. Limitations are outlined.