Background Blunt cerebrovascular injuries (BCVIs) and cervical spinal injuries (CSIs) are not uncommon injuries in patients with severe head injury and may affect patient recovery. We aimed to assess the independent relationship between BCVI, CSI, and outcome in patients with severe head injury. Methods We identified patients with severe head injury from the Helsinki Trauma Registry treated during 2015-2017 in a large level 1 trauma hospital. We assessed the association between BCVI and SCI using multivariable logistic regression, adjusting for injury severity. Our primary outcome was functional outcome at 6 months, and our secondary outcome was 6-month mortality. Results Of 255 patients with a cervical spine CT, 26 patients (10%) had a CSI, and of 194 patients with cervical CT angiography, 16 patients (8%) had a BCVI. Four of the 16 BCVI patients had a BCVI-related brain infarction, and four of the CSI patients had some form of spinal cord injury. After adjusting for injury severity in multivariable logistic regression analysis, BCVI associated with poor functional outcome (odds ratio [OR] = 6.0, 95% CI [confidence intervals] = 1.4-26.5) and mortality (OR = 7.9, 95% CI 2.0-31.4). We did not find any association between CSI and outcome. Conclusions We found that BCVI with concomitant head injury was an independent predictor of poor outcome in patients with severe head injury, but we found no association between CSI and outcome after severe head injury. Whether the association between BCVI and poor outcome is an indirect marker of a more severe injury or a result of treatment needs further investigations.