This study represents the first attempt to explore teachers' burnout experience during one of the most critical phases of the COVID-19 pandemic in Iran. The main goals were to estimate the prevalence of burnout in Iranian men and women teachers and analyse the association of sociodemographic variables on burnout levels. A total of 125 Iranian teachers participated in this study. Results suggest that Iranian teachers perceive high levels of burnout during the COVID-19 pandemic, with 24% of participants reporting high levels of overall burnout. Furthermore, 32% of the sample reported high levels of physical fatigue, 24.8% high levels of cognitive weariness, and 17.6% high levels of emotional exhaustion, suggesting that a considerable number of Iranian teachers are already struggling to deal with their job-related stressors. Significant differences were found for sex, with men reporting higher exhaustion than women. No significant differences were found between other sociodemographic characteristics and burnout. We analyse the results from a cultural perspective and discuss its implications for future research and psychological interventions in schools. Future studies explore how school contextual variables can mediate or moderate the effect of sociodemographic characteristics on teachers' burnout. Intervention programmes should consider local schools' characteristics and be sensitive to teachers' individual needs and consider the added weight of the pandemic to teachers' daily job-related stressors.