Background <p>Teachers need to know how to apply first aid measures, as children spend most of their day at school and emergencies regularly occur there. This study’s research questions are the following: to what extent do secondary school teachers in Austria have theoretical first aid knowledge specifically relevant to the school context and how do they assess their knowledge?</p> Methods <p>In all, 115 teachers who completed their teacher training in Austria and are currently teaching in Austria were included in the study. The Mann–Whitney U‑test and Kruskal–Wallis tests were used to individually test for significant differences in the results of a&#xa0;first aid quiz between different subgroups of the study population. The analysis of the self-assessments of first aid knowledge was conducted based on the relative frequencies of the individual categories of a&#xa0;five-point Likert scale.</p> Results <p>On average, 13&#xa0;out of 27 possible points (48.1%) were achieved on the theoretical first aid quiz. Subgroup analyses showed significant differences in test results regarding the teachers’ level of first aid training (<i>p</i> &lt; 0.001), the teachers’ prior experience in applying first aid techniques in the school context (<i>p</i> &lt; 0.001), and teaching science (<i>p</i> = 0.027) and STEM subjects (STEM: Science, Technology, Engineering, Mathematics; <i>p</i> = 0.004). The analysis of teachers’ self-assessments revealed that 47.9% of the participants feel not at all or only slightly competent in applying appropriate first aid measures not only independently but also correctly.</p> Conclusion <p>The participants show significant gaps in their first aid knowledge. The high percentage of uncertainty regarding the application of first aid highlights their awareness of their knowledge limitations and insecurities. An improvement of the first aid training of teachers, and thereby ensuring better preparation for potential school emergencies in the long term, would be desirable.</p>