The COVID-19 presented an unexpected event that had an immediate effect on education systems. Teachers had to make a sudden shift in their practice and adjust to this surprising and uncontrollable event. The present study explored teachers' reactions to the COVID-19 in terms of their stress response, focusing on the possible differences between Jewish and Arab teachers in Israel due to their cultural background. Nine hundred twenty-nine teachers (484 Jewish and 445 Arab teachers) completed an online survey. Using a mixed method design with a survey that included both closed and open-ended questions. Data analysis revealed that teachers in Israel were moderately stressed during this period, with Arab teachers reporting significantly higher levels of stress than did Jewish teachers. Jewish teachers were stressed mainly by personal stressors, whereas Arab teachers were stressed mainly by factors related to their professional role and by environmental factors. Arab teachers were more concerned with the reactions of school principals, Ministry of Education, and the general public than Jewish teachers, who were more concerned with uncertainty regarding the present and the future. Potential implications of the study address the importance of adapting differential solutions to support teachers according to cultural, social, and personal characteristics.