Background Trauma activation and/or leveling criteria are designed to balance the potential harm to individual patients from undertriage (UT) of severe injuries versus overutilization of resources from overtriage (OT) of lesser injuries. The American College of Surgeons (ACS) recommends an acceptable UT rate ≤5% and OT 25%-50%. To improve UT or OT, an intervention was performed to (1) improve accuracy in following established leveling criteria and (2) modify activation criteria in an evidence-based manner to better identify severely injured children. Methods Results from a prospective, interventional process improvement study performed at an ACS-verified level I pediatric trauma center are reported. The baseline period included all pediatric trauma patients who met registry inclusion criteria for 2010. The intervention period included two consecutive 3-mo periods in 2011-2012; phase I of the study involved moving the leveling responsibility from emergency department physicians to the nursing care team leaders. Phase II of the study implemented revised leveling criteria. Sustainability was assessed by evaluating data from 2014. Results In phase I, accuracy in assigned trauma activation level improved from 70% to 99%. UT decreased 10%-8%, and OT decreased 37.5%-33.3%. In phase II, UT decreased 8%-5.1%, and OT increased 33%-40%. Adherence to the activation criteria remained stable (95%). For 2014, UT was 5.3% and OT was 18.2% demonstrating sustainability. Conclusions Shifting trauma leveling responsibilities to nursing care team leaders improved accuracy. Revising the activation criteria to include Center for Disease Control and ACS guidelines, as well as tailoring the activation criteria to the program-specific population, further reduced UT rates in a sustainable fashion.