Social emotional and behavioural difficulties (SEBD) is one category of special educational needs that can have potential negative effects on children and young people (CYP) (e.g. Rusch & Chadsey, 1998; Cooper, 1999; Hallahan & Kaufman, 2000; Jull, 2008). One intervention that can be used with CYP with SEBD that draws on cognitive behavioural and solution focused approaches is the WhyTry Program (Moore, 2001), US-based studies into which have yielded largely positive effects (Eggett, 2003; Bushnell & Card, 2003; Baker, 2008; Mazzotta-Perretti, 2009; Joye & Alvarez, 2010). To date, there has been no published research into the effectiveness of this intervention in a UK context. The present exploratory process evaluation study aimed to fill this gap in the literature as well as consider implementation issues in order to strengthen the local evidence base for the intervention as part of the wider Targeted Mental Health in Schools Project (Department for Children, Schools and Families, 2008).Six male secondary age pupils formed the intervention group and three female staff co-delivered the intervention with the researcher. The intervention lasted for eleven weeks. The researcher took a mixed methods approach. Quantitative data in the form of school data and questionnaires administered to pupil participants were gathered pre- and post-intervention and at the follow-up stage. The questionnaires were the WhyTry Measure (WhyTry Organisation website), the Beck Disruptive Behaviour Inventory for Youth (Beck, Beck, Jolly & Steer, 2005) and the Beck Self-Concept Inventory for Youth (Beck et al., 2005). Qualitative data in the form of partial transcriptions of a focus group with the pupil participants and a semi-structured interview with the adult participants were gathered. A research diary was kept throughout the intervention and formed part of the data set. Quantitative data were analysed using descriptive statistics. Qualitative data were analysed using thematic analysis.This research yielded positive findings for the effectiveness of the WhyTry Program (Moore, 2001) with one group of pupils in a mainstream secondary school, as indicated by apparent improvements in pupil participants' SEBD. This study has also provided detailed information regarding the effective implementation of the intervention in the focus school, which led to the development of a context specific model of effective implementation.