The authors present process and outcome data collected during the treatment of a client seen for weekly art therapy sessions over 6 years in the UK National Health Service. Routine outcome measures completed before and after therapy with a 3-year follow-up confirmed positive therapy results. The client was part of a research study that required completing an evaluation instrument (Clinical Outcomes in Routine Evaluation Outcome Measure: CORE-OM) before each session. Retrospectively, the significance of the volume of data this produced over 6 years was recognized, and researchers collated numerical data for a single case study. At the same time, the art therapist reviewed her notes from therapy and the artwork produced by the client. Artwork was categorized by the therapist as representing different phases of therapy. After therapy ended, data from the researchers and the therapist were then systematically examined together. This study explores links between progress indicated by the CORE-OM and type of art produced, highlighting issues relating to the process, appropriateness, and cost-effectiveness of long-term therapy.