The aim of this study was to evaluate the psychometric properties of the Posttraumatic Diagnostic Scale for DSM–5 (PDS–5), a self-report measure of posttraumatic stress disorder (PTSD) based on diagnostic criteria of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders. Participants were 242 urban community residents, veterans, and college undergraduates recruited from 3 study sites who had experienced a DSM–5 Criterion A traumatic experience. The PDS–5 demonstrated excellent internal consistency (α = .95) and test–retest reliability (r = .90) and good convergent validity with the PTSD Checklist—Specific Version (r = .90) and the PTSD Symptom Scale—Interview Version for DSM–5 (PSSI–5; r = .85). The PDS–5 also showed good discriminant validity with the Beck Depression Inventory—II and the State–Trait Anxiety Inventory—Trait scale (all ZH > 3.05, ps < .01). There was 78% agreement between the PDS–5 and the PSSI–5. Receiver operating characteristic analysis yielded a cutoff score of 28 for identifying a probable PTSD diagnosis. The PDS–5 is a valid and reliable measure of DSM–5 PTSD symptomatology.