This study aimed, following both single- and multi-event trauma, to ascertain prevalence and course of the dissociative subtype of post-traumatic stress disorder (PTSD-DS) in youth; how well early PTSD-DS predicts later PTSD; and whether dissociation accounts for unique variance in post-traumatic stress symptoms (PTSS) and functional impairment over and above the effect of other post-trauma cognitive processing factors and PTSS respectively. This study is a secondary analysis of data from the Acute Stress Programme for Children and Teenagers study (n = 234) and the Coping in Care After Trauma study (n = 110) in which children had experienced single- and multi-event trauma respectively. PTSD-DS diagnosis was common in children with PTSD regardless of trauma experienced (>39.0%). PTSD-DS showed a similar trajectory of natural recovery to PTSD, and it was similarly predictive of later PTSD following single-event trauma. Finally, dissociation was a significant factor in PTSS and functional impairment. These results should be viewed in the context of several limitations including narrow sample of participants which reduces the generalizability of results, concerns around children's ability to conceptualize challenging concepts such as dissociation and the use of self-report measures to form diagnostic groups. The PTSD-DS diagnosis may offer clinical utility to the extant PTSD diagnosis in children and adolescents, as dissociation has been shown to be a contributory factor in the maintenance of both PTSS and functional impairment. Further research is required to inform further editions of the DSM and other diagnostic systems.