In this chapter, we provide an overview of emotion-focused therapy (EFT), a contemporary humanistic psychotherapy that integrates person-centered, gestalt, and existential approaches. After sketching its history and main theoretical concepts, we outline a set of emotion change principles. These guide an emotional deepening process in which therapists help clients move from undifferentiated distress to secondary reactive emotions to primary maladaptive emotions to core pain and thence to primary adaptive emotions and emotional transformation. To do this, the therapist responds to key markers offered by clients, proposing appropriate therapeutic tasks such as unfolding problematic reaction points or two-chair work for internal conflicts. In addition, we briefly summarize the relevant outcome data, review the EFT case formulation process, lay out treatment principles, consider its application to diverse client populations, and provide a brief case example