This paper provides an introductory overview of the key ideas that underpin existential psychotherapy from the primary focus of inter-relation. Further, it introduces various applications regarding the investigation of the inter-relational variables that accentuate the client’s experience of being-in-the world and considers these in relation to the analysis of the client’s presenting problems and issues. Finally, the paper argues that in the existential psychotherapeutic relationship the therapist can be likened to a particular and unique “other” in the client’s world relations.