Primary objective: This study investigated the clinical usefulness of diffusion tensor tractography (DTT) for elucidation of the corticospinal tract (CST) state in patients with transtentorial herniation (TH) following traumatic brain injury (TBI). Methods and procedures: Eleven consecutive patients with TH were recruited among 175 patients with TBI. Patients who showed TH were classified into two groups according to DTT findings: Group 1: the integrity of CST was preserved, Group 2: the integrity of CST was disrupted at the cerebral peduncle (CP) or pons. Outcomes and results: Five patients belonged to Group 1 of TH, six patients to Group 2 of TH. On DTT of Group 1, fractional anisotropy values of the CP and pons along the CST in the affected hemisphere were lower than those of the unaffected hemisphere; however, the difference was not significant (p > 0.05). In Group 2, fractional anisotropy values of the CP and pons in the affected hemisphere were significantly lower than those of the unaffected hemisphere (p < 0.05). Conclusions: It was found that DTT is useful in evaluation of the presence and the severity of CST injury in patients with TH following TBI.