Accurate assessment and effective treatment of mood disorders, particularly depression, is critically important for the millions of youth who are experiencing such symptomatology and who are at risk for a multitude of deleterious outcomes. Although the extant empirical literature provides substantial guidance for the assessment and treatment of depression, real-life complexities necessitate the inclusion of sound clinical judgment throughout the diagnostic, treatment planning and intervention phases. The purpose of this article is to present an example of a real-life case study reliant on evidence-based practices and sound clinical judgment in the assessment and treatment of depression. We first review the extant diagnostic, epidemiological, assessment, and treatment literature. The case study is intended to highlight the therapist's use of evidence-based treatment (i.e., Cognitive Behavioral Therapy), while also considering points during treatment at which the therapist was required to use clinical judgment. Outcomes of the case are described and limitations reviewed.