Trauma nurses are exposed to suffering, death and dying, and vicarious trauma, which may result in nurses experiencing posttraumatic stress disorder (PTSD). This study aims to investigate the extent of PTSD and the effect of the frequency of traumatic events, coping strategies, and social support on PTSD in South Korean trauma nurses. A cross-sectional study was conducted. Participants were 145 trauma nurses recruited from 6 regional trauma centers in Korea. The data were collected through convenience sampling using self-administered questionnaires, including the Korean version of Impact of Event Scale-Revised (IES-R-K), the frequency of traumatic events, coping strategies, and social support. The data were analyzed with descriptive statistics, t test, analysis of variance, Pearson's correlation coefficients, and multiple linear regression. The prevalence of IES-R-K score of 25 or more (indicating a high risk of PTSD) was detected in 57.2% of the trauma nurses. The frequency of traumatic events, work at traumatic emergency units, dysfunctional coping, emotion-focused coping, and social support were found to be significantly associated with PTSD. Therefore, it is necessary to develop PTSD management programs in order to provide effective coping strategies and social support for relieving PTSD symptoms. At the same time, efforts to improve the working environment are needed.