The biomechanical relationship between cranial and spinal structures makes concomitant injury likely. Concomitant craniospinal injuries are important to consider following trauma due to the serious consequences of a missed injury. The objective of this review was to estimate the prevalence of concomitant cranio-spinal injury in the adult trauma population. A systematic search of MEDLINE and EMBASE databases to identify observational studies reporting the prevalence of concomitant cranio-spinal injury in the general adult trauma population was conducted on 21 March 2017. The prevalence of concomitant cervical spinal injury in patients with a traumatic brain injury (TBI); the prevalence of concomitant spinal injury in patients with a TBI; the prevalence of concomitant TBI in patients with a cervical spinal injury; and the prevalence of concomitant TBI in patients with a spinal injury were calculated by meta-analysis. Twenty-one studies met the inclusion criteria and were included in this review. The prevalence of concomitant cervical spinal injury in patients with a TBI was found to be 6.5% (95% CI 6.0-7.1%); the prevalence of concomitant spinal injury in patients with a TBI to be 12.4-12.5%; the prevalence of concomitant TBI in patients with a cervical spinal injury to be 40.4% (95% CI 33.0-48.0%); and the prevalence of concomitant TBI in patients with a spinal injury to be 32.5% (95% CI 10.8-59.3%). This review reports the prevalence of concomitant cranio-spinal injury and highlights the importance of considering concomitant injury in patients with a cranial or spinal traumatic injury.