BACKGROUND Use of universally ABO‐compatible group AB plasma for trauma resuscitation can be challenging due to supply limitations. Many centers are now using group A plasma during the initial resuscitation of traumatically injured patients. This study was undertaken to evaluate the impact of this practice on mortality and hospital length of stay (LOS). STUDY DESIGN AND METHODS Seventeen trauma centers using group A plasma in trauma patients of unknown ABO group participated in this study. Eligible patients were group A, B, and AB trauma patients who received at least 1 unit of group A plasma. Data collected included patient sex, age, mechanism of injury, Trauma Injury Severity Score (TRISS) probability of survival, and number of blood products transfused. The main outcome of this study was in‐hospital mortality differences between group B and AB patients compared to group A patients. Data on early mortality (≤24 hr) and hospital LOS were also collected. RESULTS There were 354 B and AB patients and 809 A patients. The two study groups were comparable in terms of age, sex, TRISS probability of survival, and total number of blood products transfused. The use of group A plasma during the initial resuscitation of traumatically injured patients of unknown ABO group was not associated with increased in‐hospital mortality, early mortality, or hospital LOS for group B and AB patients compared to group A patients. CONCLUSION These results support the practice of issuing thawed group A plasma for the initial resuscitation of trauma patients of unknown ABO group.