Interest in trauma-informed approaches has grown substantially. These approaches are characterized by integrating understanding of trauma throughout a program, organization, or system to enhance the quality, effectiveness, and delivery of services provided to individuals and groups. However, variation in definitions of trauma-informed approaches, coupled with underdeveloped research on measurement, poses challenges for evaluating the effectiveness of models designed to support a trauma-informed approach. This systematic review of peer-reviewed and gray literature identified 49 systems-based measures that were created to assess the extent to which relational, organizational, and community/system practices were trauma-informed. Measures were included if they assessed at least one component of a trauma-informed approach, were not screening or diagnostic instruments, were standardized, were relevant to practices addressing the psychological impacts of trauma, were printed in English, and were published between 1988 and 2018. Most (77.6%) measures assessed organizational-level staff and climate characteristics. There remain several challenges to this emerging field, including inconsistently reported psychometric data, redundancy across measures, insufficient evidence of a link to stakeholder outcomes, and limited information about measurement development processes. We discuss these opportunities and challenges and their implications for future research and practice.