Children are exposed to distress, violence, and trauma even before they are born. In-utero and early childhood exposure can contribute to severe medical and psychological consequences. Children who have been exposed to such traumatic events often arrive at the psychotherapist’s office with emotional and behavioral symptoms suggestive of reactive attachment disorder (RAD), post-traumatic stress disorder (PTSD), and dissociation. This chapter reviews relevant theories of dissociation integrated with theories of development to provide a summary of how attachment impacts dissociation. With a developmentally grounded theory of dissociation, the chapter describes clinical interventions for treating the dissociative sequelae of attachment trauma in children. This theoretical framework offers a developmentally grounded and integrative framework for working with children with complex trauma and dissociation. Symptoms of dissociation are common with PTSD, but an extreme response to trauma can be dissociation and dissociative disorders.