The COVID-19 pandemic and quarantine measures have sparked debate regarding their traumatic nature. This cross-sectional study reports the prevalence rate of probable post-traumatic stress syndrome (PTSD) and associated factors among French university students. A total of 22,883 students completed the online questionnaire. The prevalence rate of probable PTSD, assessed using the PTSD Checklist for DSM-5, was 19.5% [19.0-20.0]. Female (1.32 [1.21-1.45]) or non-binary gender (1.76 [1.35-2.31]), exposure to a non-COVID-19-related traumatic event (3.37 [3.08-3.67]), having lived through quarantine alone (1.22 [1.09-1.37]), poor quality of social ties (2.38 [2.15-2.62]), loss of income (1.20 [1.09-1.31]), poor quality housing (1.90 [1.59-2.26]), low-quality of the information received (1.50 [1.35-1.66]) and a high level of exposure to COVID-19 (from 1.38 [1.24-1.54] to 10.82 [2.33-76.57] depending on the score) were associated with PTSD. Quarantine was considered potentially traumatic by 78.8% of the students with probable PTSD. These findings suggest the pandemic context and lockdown measures could have post-traumatic consequences, stimulating debate on the nosography of PTSD.