Emotion-Focused Therapy (EFT) is rooted in the humanistic psychotherapy tradition. A core assumption in EFT is that our life experiences are organised in emotion schemes. For instance, problematic childhood experiences that are not processed can form what are typically referred to as maladaptive emotion schemes, continuing to influence us later in in life. The goal in EFT is to activate, process and change maladaptive emotion schemes. Such a change process typically occurs through an emotional sequence, moving from secondary emotions (e.g., depressive hopelessness) through primary maladaptive emotions (e.g., maladaptive shame) to adaptive emotions (e.g., assertive anger). This sequence is termed changing emotion with emotion, and builds on substantial process research. In this article, we will describe from an EFT perspective how psychological illness arises and which conditions are necessary for it to change. We will give an account of the empirical foundation for the model and illustrate some specific interventions using the case of ‘Nadine’. Keywords: Emotion-Focused Therapy, transdiagnostic therapy, humanistic therapy, experiential therapy