The COVID-19 crisis has placed a heavy burden on medical staff and emergency workers, who may be at risk of developing psychological distress and secondary trauma. Coping and resilience to stress during a pandemic are protective factors that can mitigate the potential adverse psychological effects. Here, we investigated the direct and mediated effects of coping strategies and hardiness on secondary trauma among Italian medical staff (physicians and nurses, n = 140) and emergency workers (firefighters, civil protection, and ambulance personnel, n = 100) involved in the first phase of the pandemic. For this purpose, we collected data from participants through online questionnaires to measure emergency stress, coping strategies, hardiness, and secondary trauma. Other variables analyzed were age, sex, direct contact with COVID-19 patients, and use of personal protective equipment (PPE). We performed a correlational analysis, regressions, and a mediation analysis. The results show that nurses and physicians experienced higher levels of emergency stress than emergency workers. Direct contact with COVID-19 patients, female sex, unexpected events, and lack of PPE were risk factors for emergency stress, while resilience and coping strategies played a protective role. Mediation analysis shows that coping strategies and hardiness are protective factors and reduce the effect of stress on secondary trauma.