The high prevalence of trauma exposure and posttraumatic stress symptoms among young offenders has inspired calls for juvenile justice systems to engage in trauma-informed practices, key among which is the assessment of trauma exposure and post-traumatic reactions. Accordingly, skills in trauma assessment have become essential professional competencies for those conducting psychological evaluations in juvenile justice contexts. However, there are a number of challenges to effective practice, including the existence of two distinctly different sets of diagnostic criteria for posttraumatic stress disorder (PTSD) in the most commonly utilized diagnostic systems; controversies over the existence of separate diagnostic entities involving complex PTSD and developmental trauma disorder; difficulties with differential diagnosis and evaluating of response credibility; limited attention to diversity in traumatic stress exposure and post-traumatic reactions related to race, ethnicity, culture, gender, language, acculturation, developmental status, (dis)ability, and neurodiversity; and the need for the forensic assessment process itself to become trauma-informed, including protecting assessors from the adverse effects of secondary exposure. The present chapter reviews these challenges and offers recommendations for future research and clinical practice.