Major Depressive Disorder (MDD) is one of the more frequent disorders of adolescence and also occurs among children. In addition to the character and fitness necessary for any clinical work, clinicians who work with depressed adolescents must be competent in the areas of knowledge, assessment and treatment for this disorder. We describe basic and advanced competencies across these domains. Currently there are two evidence-based psychological interventions for adolescent depression, Interpersonal Psychotherapy and Cognitive Behavior Therapy. Basic competencies include knowledge of these interventions, of their evidence-base, and of their limitations. Associated basic assessment competencies include the skills required to conduct assessments to determine accurate diagnosis, to take into account possible co-occurring disorders, and to formulate an effective treatment plan. As clinicians move from more basic to more advanced competencies, they develop knowledge of more severe forms and possible developmental outcomes of mood disorders, including psychotic and bipolar disorders, of the diagnosis and treatment of frequent comorbid combinations, such as depression and substance abuse, and of more intensive or complex treatments, such as combined psychotherapy and medication and of inpatient care for suicidal adolescents. Within evidence-based psychotherapies, there is also a continuum of competencies, as more advanced clinicians develop a deeper understanding of and application of the treatment model, and conduct sessions that indicate an integration of the treatment model, the needs of the adolescent and the ongoing therapeutic alliance.