Purpose: The purpose of this study was to investigate the level of traumatic experiences, posttraumatic stress symptoms and mental health-related characteristics in young adults and identify relationships among the variables. Methods: In this descriptive cross-sectional study, data were collected through a Web-based survey (N=568). Structured instruments included valid measures of traumatic experiences, posttraumatic stress symptoms, depression, somatization symptoms, insomnia, and alcohol use. Collected data were analyzed using descriptive statistics, t-tests, x2 tests, ANOVA, and Pearson correlation coefficient with SPSS statistics 23. Results: Among study participants, 76.8% reported traumatic experiences. The severity of trauma was associated with high levels of posttraumatic stress symptoms, depression, somatization symptoms, insomnia, and alcohol use. Women showed more severe posttraumatic stress and depressive symptoms than men. There were positive correlations for trauma experiences with posttraumatic stress symptoms, depression, somatization symptoms, and insomnia. Conclusion: Findings indicate the need to develop nursing intervention programs to relieve posttraumatic stress symptoms and improve mental health related characteristics targeting young adults, and to establish a national policy that addresses characteristics of trauma experienced in Korea.