A psychologically informed service is one where the design, practice, and principles of the service are informed by the best understandings of the psychological and emotional needs of people who the service is intended for, with particular consideration to those who struggle to use the service in an uncomplicated way. The need for the concept of a ‘psychologically informed’ service arises because a proportion of people have psychological and emotional needs that may not be appropriately catered for within standard health and social care designs. Care-seeking is one of the most primitive and early relational dynamics we engage in. Experiences described as developmental trauma, neglect, and other mistreatment occur in relationships, often within relationships that are expected to provide safety, security, and comfort. One of the longest legacies of early relational adversity may be a loss of trust in others, which can subsequently give rise to complicated relationships with caring figures. Making a service psychologically informed can be understood as a necessary provision for those who have the highest levels of psychological need. We look at several themes to do with developing psychologically informed services: reflective practice, language used by staff, beginnings and endings of contact, time, ambivalence, and treatment.