The introduction of trauma systems has helped reduce mortality in severely injured patients. This fall in mortality, however, appears to be concentrated in higher-level trauma centres (TCs) in comparison to lower-level TCs, but the evidence is inconsistent. Therefore, we undertook a systematic review with the aim of comparing outcomes in lower-level TCs (i.e. level III and IV trauma centres) with higher-level TCs (i.e. level I and II centres). This systematic review was performed in accordance with the guidelines defined in the preferred reporting items for systematic reviews and meta-analyses statement (PRISMA). The review was registered on PROSPERO (CRD42019111933). Mortality data were combined using the Mantel-Haenszel random-effects method for meta-analysis, using Review Manager (RevMan v5.3.5). We found 28 eligible articles from an initial total of 10,816 identified abstracts. Our meta-analysis revealed no evidence of a difference in mortality risk in severely injured patients between lower-level and higher-level TCs (RR 1.55; 95% CI 0.97 to 2.50; p=0.07), but there was considerable heterogeneity (I2=92%) in the dataset. The risk of death in lower-level TCs in patients with neurological trauma, however, was statistically lower than in higher-level TCs (RR 0.80; 95% CI 0.73 to 0.86; I2=78%; p<00001). There was a higher risk of death in patients with neurological trauma managed at higher-level TCs and this is likely to be due to the higher severity of injury (intracranial and extracranial) sustained by patients at higher-level TCs. However, the high level of heterogeneity in the risk estimates of evaluated studies reduces the certainty of our interpretations.