Objective: The current study aimed to improve the content validity of the Trauma and Adverse Childhood Experiences Survey (TRACES) and the Child and Adolescent PTSD Checklist for the DSM–5 (CAPC-5). Method: Two community-based collaborative research methods were used—cognitive interviewing and focus groups. Three rounds of cognitive interviews included a racially and economically diverse sample of 12 trauma-exposed youth and 12 caregivers. Three focus groups involved 19 clinicians with diverse disciplines and years of practice. Modifications to the measures were made after each round of interviews and after completion of all focus groups. Results: Both methods provided beneficial information about issues with the measures. Feedback from youth, caregivers, and clinicians was distinct, though data across groups generally converged. Improvements were made to the measures in multiple areas, such as instructions and clarity. Conclusions: Incorporating feedback from multiple stakeholders increased the content validity of the TRACES and CAPC-5. Collaborative research methods provide a trauma-informed initial step in the development of assessment measures. (PsycInfo Database Record (c) 2022 APA, all rights reserved)