The purpose of this study was to investigate the relationship among a sense of calling, ego-resilience, and post-traumatic growth for fire officers who experience traumatic events repeatedly due to the nature of job, and to identify its influence. In particular, we tried to find out if ego-resilience plays a mediating role in the relationship between a sense of calling and post-traumatic growth. The study targeted 500 firefighters working in the metropolitan area and proceeded after obtaining approval from the Institutional Review Board of the Sacred Heart Correction (IRB) of the Catholic University for ethical consideration. First, the sense of calling was found to have a significant positive correlation with self-elasticity, and also had a significant positive correlation with post-traumatic growth. Second, ego-resilience was found to have a partial mediating effect in the process of the sense of calling affecting post-traumatic growth. This means that the sense of calling directly leads to post-traumatic growth, but also leads to post-traumatic growth through ego-resilience. Therefore, it is believed that regular programs should be prepared and implemented to counsel and treat fire officers’ mental health problems.