Objectives: The COVID-19 pandemic has forced emergency services to implement new standards of practice around the world. The dynamic and unpredictable nature of many clinical situations has placed emergency service personnel in direct danger of contracting the disease. This work uses a validated survey developed for the study to assess the predictors of stress that paramedics, nurses and doctors experience in the face of the COVID-19 pandemic. Material and Methods: The study group included 955 medical staff, and the level of significance adopted for statistical analysis was p = 0.05. Non-parametric Mann-Whitney and Kruskal-Wallis tests were used to analyze the qualitative variables divided into groups. The selection of tests was carried out based on the distribution of variables, verified using the Shapiro-Wilk test. In order to determine the predictors that caused the feelings of stress, it was necessary to use the linear regression model. Results: During the COVID-19 pandemic, stress among emergency medical personnel has increased considerably due to new factors that did not previously exist. The predictors of stress in the professional environment include the fear of contracting COVID-19, a decrease in the level of safety while conducting emergency medical procedures, and the marginalization of treatment for patients not suffering from COVID-19. Additional socio-demographic factors that increase stress among emergency medical personnel are being female and working in the nursing profession. Appropriate training, the supply of personal protective equipment and opinions on the preparedness of the system to deal with the outbreak of the pandemic did not affect the level of stress among health service personnel. Conclusions: The factors that can be considered to act as predictors of occupational stress include the fear of contracting COVID-19, a decrease in the level of safety and security while conducting emergency medical procedures, and the marginalization of patients not suffering from COVID-19. Int J Occup Med Environ Health. 2021;34(2):139–49