Few studies describe the training of student therapists in prolonged exposure (PE), an evidence-based psychotherapeutic approach to the treatment of trauma. Using a case study, this article describes training and supervision of a master-level graduate student in the implementation of PE with a research participant who had depression and posttraumatic stress disorder (PTSD) due to traumatic stress exposure. The participant’s symptom severity of depression and PTSD decreased from pretreatment to posttreatment, and symptom gains were maintained at the 3-month follow-up assessment. Implications for the training and supervision of students in the mental health professions are discussed.