This document provides an overview of attachment theory and attachment-based psychotherapy. It discusses John Bowlby's seminal work on attachment theory and patterns of secure, avoidant, resistant and disorganized attachment that develop from early caregiving experiences. These attachment patterns form internal working models that influence relationships and responses to stress throughout life. Attachment-based psychotherapy aims to provide a secure base to allow exploration and revision of internal working models, helping clients understand attachment needs and enabling therapists to respond appropriately based on clients' attachment styles.