Posttraumatic stress disorder (PTSD) assessment among transgender and gender diverse (TGD) adults is complex because the literature offers little guidance on affirming assessment that accurately captures both trauma- and discrimination-related distress. This study aimed to characterize threats to precise PTSD assessment that arose during the Clinician-Administered PTSD Scale for the Diagnostic and Statistical Manual of Mental Disorders, fifth edition (CAPS-5). Our sample (N = 44) included trans women (38%), trans men (25%), nonbinary people (23%), and other TGD identities (14%). Participants were mostly White (75%), non-Latinx (82%), educated (91% at least some college), with a mean age of 37 years (SD = 15.5). Demographic and CAPS-5 scoring data as well as content analysis of audio-recorded CAPS-5 interviews are reported. All participants reported trauma exposure, and nearly half met PTSD diagnostic criteria (49%). Interpersonal assault was a common trauma type linked to posttraumatic symptoms (77%); 41% were sexual assaults; and 41% were discrimination-based (e.g., linked to gender identity) physical or sexual assaults. Qualitative findings suggest how and when discrimination-related experiences may threaten PTSD assessment accuracy, leading to overpathologizing or underdetection of symptoms, for example, (a) initial selection of a noncriterion A discrimination event as "worst event," (b) linking symptoms to internalized transphobia (rather than trauma), and (c) linking victimization to gender identity/expression. Threats to PTSD assessment were more common when symptoms were linked to discrimination-based traumatic events, suggesting the importance of understanding contextual factors of index events. We offer a framework for understanding unique challenges to the assessment of PTSD among TGD people and provide recommendations for improving assessment. (PsycInfo Database Record (c) 2023 APA, all rights reserved).