Abstract Background School dropout is considered a serious problem in high schools in Norway. Despite studies which emphasize the importance of mental health as a unique risk factor for dropout, interventions have only taken this into account to a limited extent. Depression is one of the most prevalent mental health issues. Here we report the study protocol of a cluster randomized controlled trial of a group-CBT intervention, â Adolescent Coping with Depression Courseâ (ACDC) for depressed adolescents in upper secondary school. Method The aim of this study is to investigate the extent to which ACDC can reduce depressive symptoms, prevent dropout and improve academic and social functioning among adolescents in upper secondary school. This study investigates the effectiveness of ACDC through a cluster randomized trial, in which course leaders are randomized to experimental or control conditions where the control groups receive usual care. Discussion The intervention is expected to reduce depressive symptoms among adolescents. The study will further investigate whether the intervention can prevent dropout and improve academic and social functioning among adolescents in upper secondary school. Trial registration ISRCTN registry ISRCTN19700389 . Registered 6 October 2015.