Secondary injuries are associated with bad outcomes in the case of severe traumatic brain injury (sTBI). Patients with a Glasgow Coma Scale (GCS) < 9 should undergo pre-hospital intubation (PHI). There is controversy about whether PHI is beneficial. The aim of this study was to estimate the effect of PHI in patients after sTBI. A multicenter, prospective cohort study was performed in Switzerland, including 832 adults with sTBI. Outcomes were death and impaired consciousness at 14 days. Associations between risk factors and outcomes were assessed with univariate and multivariate Cox models for survival, and univariate and multivariate regression models for impaired consciousness. Potential risk factors were age, GCS on scene, pupil reaction, Injury Severity Score (ISS), PHI, oxygen administration, and type of admission to trauma center. Age, GCS on scene < 9, abnormal pupil reaction and ISS ≥ 25 were associated with mortality. GCS < 9 and ISS ≥ 25 were correlated with impaired consciousness. PHI was overall not associated with short-term mortality and consciousness. However, there was a significative interaction with PHI and major trauma. PHI improves outcome from patients with sTBI and an ISS ≥ 25.