This book presents a genetic-phenomenological approach of existential psychotherapy, articulating its theoretical underpinnings with principles supported by scientific evidence and concluding with clinical examples. The volume also offers a clear perspective about the relational stances and the therapeutic interventions of existential psychotherapy and how both can be combined and applied in the clinical practice. It begins with an overview and update on psychotherapy research, from which a set of therapeutic principles are drawn. It then conceptualizes the theoretical underpinnings of the genetic-phenomenological approach, based on three main aspects: inner-time consciousness, the experiential self, and the passive synthesis theory. It concludes with practical examples of case conceptualizations and clinical cases. This work is particularly relevant for trainees, students, and professionals of clinical psychology and psychotherapy, but also other mental health professionals that work in the area of the psychological and psychotherapeutic interventions.