The present study aimed to identify the contributions of sociodemographic factors, psychological hardiness, and pandemic-related stressors to the development of peritraumatic distress and posttraumatic stress symptoms (PTSS) during the peak of the COVID-19 pandemic. We also examined the mediating contribution of peritraumatic distress with respect to the associations between PTSS and (a) individual characteristics and (b) pandemic-related stressors. A total of 1,238 participants (82.1% women, 17.9% men) aged 18-75 years were included in the study. Participants completed the Dispositional Resilience Scale, Peritraumatic Distress Inventory, and Posttraumatic Stress Disorder (PTSD) Checklist. The results showed that 11.5% of participants scored above the clinical cutoff for peritraumatic distress, and 12.8% of participants scored above the clinical cutoff for PTSS. Regression models showed that higher levels of peritraumatic distress were statistically predicted by female gender, β = -.12, p < .001; exposure to more than one stressor, β = .21, p < .001; lower levels of commitment to people and activities, β = -.12, p = .002; and resistance to challenges, β = -.17, p < .001. Additionally, male gender, β = .05, p = .007; younger age, β = -.05, p = .005; lower levels of commitment to people and activities, β = -.11, p < .001; lower ratings of hardiness with regard to challenge, β = -.04, p = .043; and more severe peritraumatic distress, β = .75, p < .001, predicted more severe PTSS during the pandemic. Peritraumatic distress mediated the associations between PTSS and both the number of experienced stressors and psychological hardiness.