Defining outcome represents a key challenge for psychotherapy theory, research and practice. The present paper uses a case study of a client with anorexia nervosa to contribute to the development of conceptual understanding of the nature of paradoxical outcome. In this case, different sources of outcome data offered different answers to the question of whether or not the therapy had been successful. Qualitative thematic analysis of therapy transcriptions was carried out, using Interpretative Phenomenological Analysis (IPA). Both the process of change that occurred in this case, and the conflicting outcome indicators, could be explained in terms of a model of affect elaboration. These findings are discussed in terms of the need for caution when interpreting results from outcome measures in psychotherapy research and practice.