Objective: The inclusion of a dissociative subtype in the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5) criteria for the diagnosis of posttraumatic stress disorder (PTSD) has highlighted the need for valid and reliable measures of dissociative symptoms across developmental periods. The Adolescent Dissociative Experiences Scale (A-DES) is 1 of the few measures validated for young persons, but previous studies have yielded inconsistent results regarding its factor structure. Further, research to date on the A-DES has been based upon nonclinical samples of youth or those without a known history of trauma. To address these gaps in the literature, the present study investigated the factor structure and construct validity of the A-DES in a sample of highly trauma-exposed youth involved in the juvenile justice system. Method: A sample of 784 youth (73.7% boys) recruited from a detention center completed self-report measures of trauma exposure and the A-DES, a subset of whom (n = 212) also completed a measure of DSM–5 PTSD symptoms. Results: Confirmatory factor analyses revealed a best fitting 3-factor structure comprised of depersonalization or derealization, amnesia, and loss of conscious control, with configural and metric invariance across gender. Logistic regression analyses indicated that the depersonalization or derealization factor effectively distinguished between those youth who did and did not likely meet criteria for a diagnosis of PTSD as well as those with PTSD who did and did not likely meet criteria for the dissociative subtype. Conclusions: These results provide support for the multidimensionality of the construct of posttraumatic dissociation and contribute to the understanding of the dissociative subtype of PTSD among adolescents.