Introduction: The effectiveness of massive transfusion protocols (MTPs) has been assumed from low quality studies with multiple biases. This review aimed to (i) evaluate the association between the institution of an MTP and mortality and (ii) determine the effect of MTPs on transfusion practice post trauma. Methods: A systematic review of studies that examined patient outcomes before and after the institution of an MTP in the same centre was conducted. The design and results of each study were described. Heterogeneity was assessed using the Q test and the I2 statistic. Odds ratios (ORs) for dichotomous outcomes from each study were pooled. Results: There were eight studies that satisfied inclusion criteria with marked heterogeneity in study populations (I2 = 72.1 , P = 0.001). Two studies showed significantly improved mortality following implementation of an MTP, and six studies showed no significant change. Pooled OR for the effect of an MTP on short-term mortality was 0.73 (95 confidence interval: 0.48-1.11). The effect of MTPs on transfusion practice was varied. Conclusion: Despite the popularity of MTPs and directives mandating their use in trauma centres, in before-after studies, MTPs have not always been associated with improved mortality. Evidence-based standardization of MTPs, improved compliance and analysis of broader endpoints were identified as areas for further research.