© 2019 Kure Iletisim Grubu A.S.. All rights reserved.The aim of this study was to explore whether DSM-5 posttraumatic stress disorder (PTSD) dissociative subtype could be differentiated from non-dissociative PTSD caseness in sleep disturbances, circadian preferences, and posttraumatic cognitions. We also investigated associations of dissociation, sleep quality, insomnia, circadian preferences, and traumarelated negative cognitions with DSM-5 PTSD caseness among prisoners. Data from 399 volunteers (mean age: 34.54±9.93 years) were collected. Using the symptoms clusters measured by the PTSD Checklist for DSM-5 (PCL-5) and Dissociative Experiences Scale (DES), the participants were classified into four subgroups: no dissociation or PTSD, pure dissociative, pure PTSD, and dissociative PTSD. Differences in scale scores across four groups were evaluated using one-way analysis of variance. Logistic regression analysis was utilized to determine predictors of DSM-5 PTSD caseness. Participants with dissociative PTSD reported significantly greater posttraumatic stress reactions in terms of PTSD and dissociative symptomatology, greater number of prior trauma exposure, greater scores on posttraumatic negative cognitions, and a tendency to have eveningness diurnal preferences in comparison to those prisoners classified into other three subgroups (no dissociation or PTSD, pure dissociative, and pure PTSD). However, sleep disturbances in terms of insomnia and poor sleep quality were found to be pronounced among prisoners with PTSD irrespective of levels of dissociation. Dissociative symptomatology, insomnia and poor sleep quality significantly contributed to probable PTSD caseness. Dissociation and sleep disturbances appear to be hallmark for PTSD among prisoners.