This paper describes descriptive research to identify the effects of job stress, COVID-19 self-care behavior, and COVID-19 vaccination status according to the infection and non-infection of COVID-19 on anxiety about the COVID-19 infection among firefighters in South Korea. Data from 205 firefighters working at 10 fire stations were collected from 26 January to 16 February 2023. The variables used were job stress, COVID-19 self-care behavior, COVID-19 vaccination status, and COVID-19 infection anxiety. The collected data were analyzed using descriptive statistics,t-test, one-way ANOVA, Pearson’s correlation coefficient, and multiple linear regression. In subjects who were infected with COVID-19, the factors that significantly affected infection anxiety were job stress (β = 0.247,p= 0.011) and self-care behavior (β = 0.343,p= 0.011). In subjects who were not infected with COVID-19, the factors that significantly affected infection anxiety were marriage status (unmarried) (β = −0.260,p= 0.005) and self-care behavior (β = 0.374,p= 0.001). These results demonstrate that the infection anxiety of firefighters should be prevented, and their physical and mental health should be promoted by considering job stress, self-care behavior, and personal environment.