Triple P is a parenting programme used in the youth healthcare practice of many Dutch municipalities to support parents in raising their children. According to international research, this Australian intervention is effective for parents with children up to the age of 12. It shows positive effects on parenting skills and on the reduction of both parents' child-rearing stress and their children's behavioural and emotional problems. Our study examined the effectiveness of Teen Triple P level 4: a training programme for parents of teenagers aged 10–16. The programme included five group sessions of 1.5–2 h each, as well as three individual (phone) consultations. Through a matching procedure, 103 parents who participated in Teen Triple P were compared in a quasi-experimental study with 397 parents in a control group. Compared with the control group, parents who received the Teen Triple P training reported a significant improvement in their parental practice. Now, they are more involved with their child, more responsive to the needs of the children, and they report fewer parent–child conflicts. Some positive differences in behavioural problems among adolescents, as reported by their parents, could be found among the experimental group. These findings remained the same at the follow-up.