Background & Aims Coronavirus disease 2019 (COVID-19) caused many psychological and social problems in people around the world, especially nurses. The present study aims to investigate and compare post-traumatic stress disorder (PTSD), burnout, and psychological disorders in nurses with and without COVID-19. Materials & Methods This is a causal-comparative study. The study population includes all male and female nurses of non-government hospitals in Tehran from July to September 2021. Of these, 220 nurses (110 without COVID-19 infection and 110 with COVID-19) voluntarily participated in the study. The questionnaires were the Mississippi Scale for Combat-Related Post-Traumatic Stress Disorder, the Maslach Burnout Inventory, and the Depression, Anxiety, Stress Scale. Finally, data analysis was performed using multivariate and univariate analysis of variance in SPSS software, version 16. Results There was a significant difference between the two groups in terms of PTSD, burnout, and psychological disorders (P<0.05). Nurses with COVID-19 had higher scores in PTSD (F=96.38, P<0.001), emotional exhaustion (P<0.001, F=12.45), depersonalization (F=15.49, P<0.001), depression (F=92.97, P<0.001), anxiety (F=37.94, P<0.001) and stress (F=47.6, P<0.001). The nurses with no COVID-19 had higher score in personal accomplishment. Conclusion Nurses who were infected with COVID-19 had lower psychological health compared to non-infected nurses. For this purpose, it is necessary to take measures to identify and provide psychological treatments to improve the mental health of vulnerable nurses.