Aims: This paper describes the application of a clinical cognitive behavioural therapy (CBT) intervention with an adolescent in a further education setting who was experiencing low mood and anxiety. Method: A retrospective single case study design was used based on data collected from outcomes and systematic feedback measures previously administered throughout the course of therapy. Qualitative data were also gathered including: reflections within a therapeutic diary, case notes, materials from the therapy, and a narrative summary detailing the implementation of therapy. This information was triangulated with records of session by session feedback measures to examine the relationship between the process of implementation in therapy and the young person's idiographic responses. Findings: Outcome measures derived from the intervention suggest that it was of limited effect in improving the young person's symptoms of low mood and anxiety. Variability in markers of progress between sessions was associated with factors of change, including divergences in expectancy between the educational psychologist (EP) in the role of therapist, motivational factors, systemic and extra-therapeutic factors. Conclusions: Findings underscore the importance of considering factors for change such as therapist, expectancy, relationship, technique, and extra-therapeutic based factors in the implementation of therapy with post-16 populations. This supports implementation research indicating that there is considerable room to engage individuals with the process of CBT and integrate motivational and systemic factors into decision making about therapy. Implications for research and educational psychology practice are discussed.