BACKGROUND: Massive transfusion protocols (MTPs) to address hemorrhage are understudied in children. The objective was to determine the effect of MTP implementation on outcomes of injured children. STUDY DESIGN AND METHODS: This was a retrospective comparison of injured children before and after MTP implementation for children less than 18 years old who presented in 2005 to 2014 and received red blood cells (RBCs) within 24 hours of arrival. Children were divided into groups based on pre-/post-MTP implementation and subgrouped based on receipt of massive transfusion (≥40 mL/kg RBCs or ≥80 mL/kg total blood products at 24 hr from arrival). The primary outcome was in-hospital mortality and secondary outcomes were total blood product use, intensive care unit/ventilator/pressor-free days, composite morbidity, and Glasgow Outcome Score. RESULTS: A total of 11,995 children presented for trauma care over 9 years; 235 received RBCs. A total of 120 were in the pre-MTP group and 115 in the post-MTP, of whom 26 and 17 received massive transfusion in the pre- and post-MTP groups, respectively; 11 had MTP activations. Children massively transfused after MTP received mean plasma:RBC and platelet (PLT):RBC ratios greater than 1:1 at both 6 and 24 hours with no significant difference in total admission blood product use. There was no difference in in-hospital mortality between pre- and post-MTP groups (24% vs. 19%) or massive transfusion subgroups (54% vs. 47%). There were no differences in secondary outcomes. CONCLUSIONS: While we were not able to show improvements in outcome, MTP implementation led to higher plasma and PLT:RBC ratios without an associated change in blood product use or composite morbidity.