Firefighters are among the first groups who deal with injuries from accidents. They are significantly at risk for disorders such as PTSD. This study aimed to compare the cognitive performance, mood and emotion regulation in firefighters with and without PTSD. This study, from July to October 2016, utilized a descriptive, causal-comparative approach and the statistical population consisted of all firefighters in Isfahan. The selection criterion in this study was work experience for one consecutive year. The sample included 40 firefighters with and without post-traumatic stress disorder (PTSD) selected by a random cluster sampling. In so doing, 11 fire stations in Isfahan were randomly selected from 24 stations. The firefighters at each of these stations were divided into two groups; with PTSD and without PTSD, based on their answers to the Mississippi questionnaire. The measuring instruments were the Color Tracking Test, the London Tower test, subscales of the Wechsler memory test, Beck Depression Inventory, and Garnofsky’s Emotion Regulation questionnaires. The collected data were analyzed by SPSS 22 software by Mean Standard Deviation analysis, Shapiro-Wilk’s normality, and multivariate analysis of variance ANOVA tests. The results showed that there were significant differences between the scores of cognitive performance, mood and emotion regulation in firefighters with and without PTSD (p< .01). In addition, there were significant differences in firefighters, with and without PTSD (p< .01), between the scores of the time and error in first-try of attention, B and C levels of executive functions, digit span total score and forward digit span of working memory, mood and subscales of emotion regulation including positive re-evaluation, reaching a perspective and subjective rumination.