Background: Manualized cognitive-behavioural therapy (MCBT) approaches to treating adolescent anxiety and depression have been shown to be effective in recent years, as have MCBT for adult self-harm (SH). Aims: This paper describes the rationale for, development and pilot evaluation of the efficacy of a novel manualized CBT package for adolescent self-harm (SH). It also addresses the acceptability of this treatment package to therapists and patients. Method: Twenty-five adolescents (aged 12–18 years) presenting to a Community Child and Adolescent Mental Health Service (CAMHS) in Greater London with SH behaviour began the “Cutting Down” programme and 16 (64%) completed the treatment. Outcomes were assessed at baseline, at the end of treatment and at 3 month follow up. Results: Significant reductions in self-harm behaviour, depression symptoms and trait anxiety were reported. There was no change in state anxiety or in levels of parental expressed emotion as perceived by the adolescent. Conclusion: These pilot findings provide preliminary support for the efficacy and acceptability of this time-limited CBT package for adolescents who self-harm.