Objectives: Cultural variations complicate psychiatric care, especially for migrant children. Transcultural psychotherapy (TCP) is an original psychotherapeutic technique developed to address complex situations of resistant mental disorders in the context of migration. This research will aim to assess the efficacy, the acceptability, and describe the therapeutic processes of TCP for the treatment of depression in first or second generation of migration children and adolescents. Method: Mixed method study using a multicenter, Bayesian randomized clinical trial with blinded evaluation of the primary outcome. Two parallel groups of 40 children or adolescents from 6 to 20 years old and their family will be included. In the experimental group, patients will attend six sessions of transcultural therapy in addition to usual care. Results: The improved Clinical Global Impression scale scores at 6 months will be compared across groups. Qualitative analysis of families and therapists' interviews will allow to specify the therapeutic processes and acceptability of the therapy. Conclusion: The findings will encourage the development and routinization of TCP for second-line use and its adaption as a first-line technique in this population. K E Y W O R D S child, depression, mixed method, transcultural, treatment 1 | INTRODUCTION Migrant children represent 9.4% (47.3 million) of the European population and come, for a large part, from low-and middle-income countries. In France, one in three children born has at least one parent who comes from elsewhere and 17% of children under 18 are migrants (INSEE, 2016). This proportion continues to rise and as they may differ in physical appearance, language, religion, and culture from the nonmigrant population (Hernandez, 2010), psychiatric care of immigrated families constitutes a growing challenge in many