This study is a first-level evaluation of an intervention targeted at adolescents with social, emotional and behavioural difficulties in Irish post-primary schools. It is a combined implementation of the Working Things Out adolescent programme and the Parents Plus Adolescent Programme (WTOPPAP). Overall, 47 parents and their children (mean age: 13.81 years) took part in the study. The study used a repeated measures design to assess change at pre- and post-intervention and 5-month follow-up using the Strengths and Difficulties Questionnaire, McMaster General Functioning Scale, Goal Attainment (parent- and adolescent-rated), Parent Stress Scale and Kansas Parenting Satisfaction Scale (parent-rated) as assessment measures. This study found that parent-rated child total difficulties and adolescent-rated emotional difficulties significantly improved from pre-test to 5-month follow-up. Parent- and adolescent-rated goals, and parent-rated child conduct difficulties, parental stress and satisfaction with parenting also significantly improved from pre- to post-test. These gains were largely maintained at 5-month follow-up. These findings indicate that the WTOPPAP may be an effective intervention for adolescents with emotional and behavioural difficulties and their parents. It was demonstrated that a manualised family intervention could be effectively rolled out at a number of school locations, with delivery and evaluation being conducted by school staff. Further implications are also discussed.