Despite the evidence linking chronic early trauma with psychological distress, the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) has excluded developmental trauma disorder from its taxonomy. This article considers developmental trauma from an attachment-based perspective and raises some of the difficulties professionals may experience conceptualising the trauma–attachment relationship. It explores the impact of the decision to exclude the diagnosis from DSM-5 on professionals, those who have had traumatic early experiences and their carers. Finally, it presents formulation as an alternative proposition which may better suit those who present to mental health services with attachment- and trauma-linked difficulties.