© 2021 The Korean Neurosurgical Society.Objective: We aimed to investigate the presence of brachial plexus injury (BPI) in traumatic brain injury (TBI) patients and to draw attention to BPI, which can be overlooked by physicians in TBI patients. Methods: The study was designed retrospectively by examining the files of 58 patients with moderate to severe TBI to investigate coexistence of TBI and BPI. Results: BPI was detected in six of 58 TBI patients (10.3%). BPI was detected after an average 116 days from the initial injury. Three patients had lower trunk BPI and three patients had panplexopathy. Conclusion: Diagnosis of BPI in patients with TBI is delayed in the acute period of injury. The clinicians should keep in mind that BPIs may occur and remain undiagnosed in patients with TBI.