ObjectiveTo determine whether high-frequency repetitive transcranial magnetic stimulation (rTMS) improves cognition in patients with severe traumatic brain injury.MethodsA single-center, randomized, double-blind, placebo-controlled study of rTMS was conducted in patients aged 18–60 years with chronic (>12 months postinjury) diffuse axonal injury (DAI). Patients were randomized to either a sham or real group in a 1:1 ratio. A 10-session rTMS protocol was used with 10-Hz stimulation over the left dorsolateral prefrontal cortex (DLPFC). Neuropsychological assessments were performed at 3 time points: at baseline, after the 10th rTMS session, and 90 days after intervention. The primary outcome was change in executive function evaluated using the Trail Making Test Part B.ResultsThirty patients with chronic DAI met the study criteria. Between-group comparisons of performance on TMT Part B at baseline and after the 10th rTMS session did not differ between groups (p = 0.680 and p = 0.341, respectively). No significant differences were observed on other neuropsychological tests. No differences in adverse events between treatment groups were observed.ConclusionsCognitive function in individuals with chronic DAI is not improved by high-frequency rTMS over the left DLPFC, though it appears safe and well-tolerated in this population.ClinicalTrials.gov identifierNCT02167971.Classification of evidenceThis study provides Class II evidence that for individuals with chronic DAI, high-frequency rTMS over the left DLPFC does not significantly improve cognition.