Compared to other occupations, firefighters experience profound physical and psychological demands, which put them at risk for Posttraumatic Stress Disorder (PTSD). However, the available research indicates that there is a large variability in the percentage of firefighters who develop symptoms of PTSD that can be accounted for by resiliency factors. The purpose of this study is to investigate what factors predict the development of PTSD symptomatology. To achieve this aim, the Posttraumatic Stress Disorder Checklist (PCL-C) and the Conner-Davidson Resilience Scale (CD-RISC), were administered to 127 full-time firefighters. A linear regression analysis was conducted. The results indicate that those with higher scores on the CD-RISC and the amount of calls per shift predict PCL-C scores. This study has important implications for developing prevention programs for the development of PTSD symptomology in firefighters that monitor the number of calls firefighters receive per shift, as well as identifying resiliency areas for improvement based on routine administration of the CD-RISC. Given the high stress situations that first responders experience, empirical research in this field needs to be advanced.