IntroductionNo evaluated therapeutic approaches, that can efficiently be established in routine mental healthcare, are currently available for traumatised adolescent refugees in Germany. This study evaluates the efficacy of the Stress-Traumasymptoms-Arousal-Regulation-Treatment (START) programme to reduce trauma-related symptoms and psychological distress in traumatised adolescent refugees based in Germany.Methods and analysisThis randomised, waiting-list-controlled, multicentre trial with a 12-week follow-up will include 174 refugee minors with partial or full post-traumatic stress disorder who are fluent in either Arabic, Dari, English, German or Somali. Eligible refugee minors will be randomised to the START or waiting-list control groups. The manualised 8-week START programme is based on techniques of dialectical behaviour therapy (DBT), fosters adaptive coping with emotional distress and traumatic symptoms and comprises eight therapy modules and a booster session. Study assessments are planned at baseline, post-treatment (ie, after programme participation or waiting time), booster session at week 12 or 12-week waiting time, and at the 12-week follow-up. Primary and coprimary outcomes are changes in psychological distress and traumatic symptoms at post-treatment and will be analysed as response variables in linear mixed regression models. Secondary outcomes are changes in further trauma-related and other psychopathological symptoms, emotion regulation and intermediate effects of the programme at follow-up. We will also assess effects of the programme with ecological momentary assessments and on neuroendocrine stress parameters using hair cortisol.Ethics and disseminationThis study has been approved by the lead ethics committee of Rhineland-Palatinate and the ethics committees of participating sites. The study results will be disseminated through peer-reviewed publications and scientific conferences.Trial registration numberDRKS00020771.