Open access. Mentalization Based Therapy (MBT) has yielded promising outcomes for reducing self-harm, although to date only one study has reported MBT’s effectiveness for adolescents (Rossouw and Fonagy, J Am Acad Child Adolesc Psychiatry 51:1304–1313, 2012) wherein the treatment protocol consisted of an intensive programme of individual and family therapy. We sought to investigate an adaptation of the adult MBT introductory manual in a group format for adolescents.