Abstract Background Depression is a serious disorder in childhood and adolescence. Affected children and adolescents show significant impairments in various aspects of life. Studies on the effectiveness or efficacy of psychotherapy in depressed children and adolescents are qualitatively very heterogeneous and reveal small effect sizes. There is thus a need to better tailor psychotherapy approaches to these age groups to improve outcomes like parent-child relationship, symptomatology, or quality of life. To address this gap, we designed a modular, individualized treatment program for children and adolescents based on the Cognitive Behavioral Analysis System of Psychotherapy (CBASP) including caregiver involvement. Method This quasi-experimental pilot feasibility trial is a phase 1 to phase 2 study investigating the feasibility and effectiveness of CBASP@YoungAge by including an intervention group (CBASP@YoungAge) and a treatment-as-usual control group. The treatment of depressive symptoms as well as interpersonal problems with primary caregivers are the main targets of CBASP@YoungAge. Personalization is ensured concerning the treatment course, caregivers’ involvement, and the patient’s age. The primary outcome relates to two areas: the feasibility of the CBASP@YoungAge treatment program in an outpatient context and a change in patients' depressive symptomatology from before to after treatment. We conduct a brief process evaluation after each session in the intervention group to closely monitor the treatment process and examine feasibility from the therapists' and patients' perspectives and mechanisms of symptom change. In addition, we consider interpersonal behavior between children and caregivers, parenting behavior, and monitor the global-health-index in children and parents as secondary outcomes. Pre-, post-, and follow-up data are evaluated. Discussion This is the first study of a modular-based intervention program for children and adolescents with depression and a clear focus on the interpersonal problems between the depressed young patient and her/his caregiver. It will provide important knowledge on the feasibility and effectiveness of the program and potential benefits of including caregivers in psychotherapy. Based on this study’s results, we plan a multicenter, randomized, controlled trial whose long-term aim is to improve the psychotherapeutic care of young patients with depression while preventing persistent courses of depressive disorders. Trial registration German Clinical Trials Register, DRKS (identifier DRKS00023281). Registered 17 November 2020–Retrospectively registered