Trauma has received a great deal of attention in recent years. One line of research in this field focuses on the importance of personality variables in the resistance and vulnerability to trauma (Figley, 1995) and on the consequences of trauma on emergency professionals (Stamm, 2002). The purpose of this study was to examine in a sample of 419 emergency professionals the role of several personality variables (empathy, comprehensibility, challenge and sense of humor) as moderators of the relationship between job demands (traumatic task and overload) with shattered assumptions (Janoff-Bulman, 1992). Secondary traumatic stress was measured with measured with Secondary Traumatic Stress Measure (Moreno et al., 2004). Results indicate these personality variables seem to have an important role in the change of assumptions process. Finally, further implications of the findings are discussed.