Childhood adversity is common in the lives of individuals with intellectual disabilities (ID) within secure forensic placements, and is not currently well recognized are post-traumatic stress disorder (PTSD), complex PTSD (CPTSD), and Developmental Trauma Disorder (DTD). A two-stage assessment framework was employed in this study to evaluate the prevalence, clinical correlates and dysregulation profiles of adults detained in secure forensic ID services who had PTSD, CPTSD, and DTD-consistent symptomatology. A cross-sectional quantitative design was used across low, medium and high secure forensic ID services, (N=150). The Trauma Screener–ID was used to screen participants in Stage 1. Structured diagnostic evaluations were provided for Stage 2 with the Impact of Event Scale-Intellectual Disabilities (IES-IDs), International Trauma Questionnaire-Intellectual Disabilities (ITQ-IDs), and Diagnostic Interview Trauma and Stressors-Intellectual Disabilities (DITS-IDs). Overall point prevalence for probable ICD-11 trauma disorders was 32.0% (n=48, 95% CI [24.6%, 40.1%]), comprising 14.0% PTSD (n=21) and 18.0% CPTSD (n=27). Another 13.3% (n=20) had sub-threshold core symptoms of PTSD and a significant multi-domain dysregulation in accordance with the DTD. Two-stage trauma screening is viable in secure ID care and results in significant amount of undetected trauma. These results have clinical implications for the need to move away from reactive risk containment approaches to routine multi-stage trauma-informed forensic ID assessment pathways. It is imperative to systematically identify these hidden trauma profiles in order to minimize the length of stay in institutions, the use of restrictive behavioral management practices, and the use of psychological intervention that is formulated and targeted to address complex developmental needs.