ImportanceReducing low-value care has the potential to improve patient experiences and outcomes and free up health care resources. Sixteen quality indicators were recently developed targeting reductions in low-value trauma care based on a synthesis of the best available evidence, expert consensus, and patient preferences.ObjectiveTo assess the validity of quality indicators on low-value trauma care using trauma registry data.Design, Setting, and ParticipantsData from an inclusive Canadian provincial trauma system were used in this analysis. Included were all admissions for injury to any of the 57 provincial adult trauma centers between April 1, 2013, and March 31, 2020. Metrics for quality indicators were developed iteratively with clinical experts.Main Outcomes and MeasuresValidity was assessed using a priori criteria based on 5 parameters: frequency (incidence and case volume), discrimination (interhospital variation), construct validity (correlation with quality indicators on high-value care), predictive validity (correlation with quality indicators on risk-adjusted outcomes), and forecasting (correlation over time).ResultsThe study sample included 136 783 patient admissions (mean [SD] age, 63 [22] years; 68 428 men [50%]). Metrics were developed for 12 of the 16 quality indicators. Six quality indicators showed moderate or high validity on all measurable parameters: initial head, cervical spine, or whole-body computed tomography for low-risk patients; posttransfer repeated computed tomography; neurosurgical consultation for mild complicated traumatic brain injury; and spine service consultation for isolated thoracolumbar process fractures. Red blood cell transfusion in low-risk patients had low frequency but had moderate or high validity on all other parameters. Five quality indicators had low validity on at least 2 parameters: repeated head CT and intensive care unit admission for mild complicated traumatic brain injury, hospital admission for minor blunt abdominal trauma, orthosis for thoracolumbar burst fractures, and surgical exploration in penetrating neck injury without hard signs.Conclusions and RelevanceThis cohort study shows the feasibility of assessing low-value trauma care using routinely collected data. It provided data on quality indicators properties that can be used to decide which quality indicators are most appropriate in a given system. Results suggest that 6 quality indicators have moderate to high validity. Their implementation now needs to be tested.