BACKGROUND:Prior research has reported an association among trauma patients between blood type O and adverse events. More recently, another study reported that severely injured trauma patients of mostly O Rh positive blood type were more likely to die. OBJECTIVE:The objective of the current study is to examine whether the same increased association is observed for blood type O severely injured patients in a more generalizable population comprised of Rh positive and Rh negative individuals. METHODS:Patients admitted to a Level-I academic trauma center between 2015 and 2018 with severe injury (Injury Severity Score >15) were included in this retrospective cohort study. Logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs) for the association between blood type and mortality. RESULTS:Among 3,913 patients, a majority were either blood type O (47.5%) or A (34.7%) and 60% were Rh positive. There was no observed difference in complication rates by blood type, and there was no observed significant association with death overall or by cause of death. There were weak, increased associations for blood type B (OR 1.61, 95% CI 0.74–3.53) and type O (OR 1.57, 95% CI 0.90–2.76) compared with blood type A patients. CONCLUSION:Contrary to prior research, the current results suggest no association between blood type and mortality among severely injured trauma patients.