Since March 2020, the COVID-19 pandemic has become a global concern, affecting students' mental health. This study aims to explore the prevalence of post-traumatic stress disorder (PTSD), and sleep disturbance among Vietnamese students during the fourth COVID-19 wave. An online survey was performed with a questionnaire based on the Impact of Event Scale-Revised scale (IES-R). A total of 302 students were included in the study, in which there are 11.3% had PTSD. The prevalence of PTSD in female was higher than in male (p=0.006) and students who were fear of vaccine's side effects had five times higher likelihood of PTSD compared to those who were not (p=0.009). In addition, changes in bedtime and wake-up times were associated with increased odds of PTSD in students (Adjusted Odds Ratios: 3.42, 95% Confidence Intervals: 1.90 to 6.16). The results emphasize the high prevalence of PTSD among students, which could have short- and long-term mental health impacts.