Objective Several previous studies have reported the negative psychological impact of the coronavirus disease (COVID-19) pandemic on medical students worldwide. This study investigated the sociodemographic and psychosocial factors associated with COVID-19-related post-traumatic stress disorder (PTSD) risk among medical students in Daegu, a region that experienced a high concentration of infections. Methods A total of 270 students completed the self-reported questionnaires including COVID-19 exposure, psychological measurement, and sociodemographic factors. We evaluated the COVID-19-related PTSD risk group using the Korean version of the Impact of Event Scale-Revised. Logistic regression analysis was performed to evaluate the odds ratio for the COVID-19-related PTSD risk group in sociodemographic and psychosocial factors. Results The prevalence of the COVID-19-related PTSD risk group was 10.4% in medical students. Among sociodemographic factors, lower grades (specially, first-year medical students) and current smokers were associated with the COVID-19-related PTSD risk. Indirect exposure to COVID-19 was also associated with this risk. Meanwhile, having higher resilience, self-esteem, and social support were less likely to be associated with COVID-19-related PTSD risk. Conclusion This study suggested that it is necessary to develop a system for the screening and managing of COVID-19-related PTSD risk group among medical students, especially high-risk groups during the COVID-19 pandemic.