IntroductionFirefighters repeatedly encounter traumatic and stressful events while on duty, leading to mental disorders such as post-traumatic stress disorder symptoms (PTSS). This disorder can affect the rate of cognitive failures (CFs) and thus increase the probability of human error, unsafe behaviors, and accidents. The present study was conducted to investigate the direct and indirect effects of trauma load on the rate of CFs in firefighters and to investigate the mediation effect of PTSS and the moderation effect of resilience, neuroticism, and job characteristics. MethodsThe study was performed by cross-sectional design in 2020 on all operational firefighters from Hamadan, Iran. A total number of 240 firefighters made up the sample size of our study. Data were collected using validated questionnaires during nine months. Hypothesis testing and data analysis were performed using structural equation modeling (by Amos software version 24) and hierarchical regression (by the 23rd version of SPSS software). ResultsPTSS fully mediated the relationship between trauma load and CFs. Trauma load, resilience, and neuroticism were significant predictors of PTSS (p<0.05). Resilience and neuroticism had no moderation effect on the relationship between trauma load and PTSS (p>0.05). PTSS showed a direct relationship with CFs (p<0.001). Among job characteristics, only job control moderated the relationship between PTSS and CFs (p<0.05). Conclusiontrauma load can increase the rate of CFs by causing PTSS in firefighters. High job control at work can weaken the relationship between PTSS and CFs.