A structural equation model was used to investigate the relationship between trauma exposure and comorbid mental health problems and the mediation effect of posttraumatic stress disorder (PTSD) between trauma and mental health variables. The research model is based on the stress-vulnerability conceptual framework in which PTSD as a comorbid disorder mediates the relationship between trauma exposure and mental health problems. A self-administered survey was administered to 144 North Korean refugee youth residing in South Korea. Trauma exposure, both interpersonal and noninterpersonal, had no direct relationship with comorbid mental health problems. However, interpersonal trauma contributed to comorbid mental health problems through PTSD, demonstrating the mediation effect of PTSD and supporting the stress-vulnerability hypothesis of the current research model. Clinical implications of the study and future direction for research are discussed.