The work environment of emergency workers is an important factor related to stress. Coping with the COVID-19 emergency is a factor that is highly related to stress, and severe stress is a risk factor for developing secondary trauma. Coping and resilience can help rescue workers to better respond in emergency situations and could protect them from secondary trauma. We aimed to explore the relationship of emergency stress, hardiness, coping strategies, and secondary trauma among emergency workers and the mediating roles of coping strategies and hardiness on the effect of stress in producing secondary trauma. The study involved 513 emergency workers from the Red Cross Committee in Veneto, one of the Italian regions most affected by the COVID-19. Participants completed questionnaires online to measure emergency stress (physical, emotional, cognitive, organizational‒relational, COVID-19, and inefficacy decisional), hardiness, coping strategies, and secondary trauma. Other variables analyzed were age, gender, weekly hours of service, and use of personal protective equipment (PPE). We performed t-tests, a correlational analysis, regressions, and a mediation analysis. Hardiness and coping strategies, in particular, which stop unpleasant emotions and thoughts and problem-focused, emerged as mediators in reducing the predicted effect of stress on secondary trauma. The mediating effects of hardiness and coping strategies were found to reduce the effect of stress on arousal by 15% and the effect on avoidance by 25%.