Objective : Post-traumatic stress disorder (PTSD) is a group of diseases that are observed in patients who had experienced a serious trauma or accident. However, some experienced it even after only a mild traumatic brain injury (TBI), and they are easily ignored due to the relatively favorable course of mild TBI. Herein, the authors investigated the incidence of PTSD in mild TBI using brief neuropsychological screening test (PTSD checklist, PCL). Methods : This study was conducted on patients with mild TBI (Glasgow coma scale ${geq}13$) who were admitted from January 2012 to December 2012. As for PCL, it was done on patients who showed no difficulties in communication upon admission and agreed to participate in this study. By using sum of PCL, the patients were divided into high-risk group and low-risk group. PTSD was diagnosed as the three major symptoms of PTSD according to the Diagnostic and Statistical Manual of Mental Disorders, fourth-edifion. Results : A total of 314 TBI patients were admitted and 71 of them met the criteria and were included in this study. The mean age was 52.9 years-old (range : 15--94). The mean PCL score was 28.8 (range : 17--68), and 10 patients were classified as high-risk group. During follow-up, 2 patients (2.7%) of high risk group, were confirmed as PTSD and there was no patient who was suspected of PTSD in the low-risk group (p=0.017). Conclusion : PTSD is observed 2.8% in mild TBI. Although PTSD after mild TBI is rare, PCL could be considered as a useful tool for screening of PTSD after mild TBI.