To highlight effective levers to promote teachers’ wellbeing worldwide, particularly during difficult times such as the COVID-19 pandemic, we investigated work-related factors associated with teacher wellbeing, across borders and cultures. In six countries/territories, we examined the factors that were most consistently and strongly associated with two indicators of wellbeing at work: (i) job satisfaction; and (ii) work/life balance, and three indicators of general wellbeing: (i) subjective health; (ii) mental health; and (iii) life satisfaction. Between May and July 2021, after 18 months of the pandemic, 8000 teachers answered the first edition of the International Barometer of Education Personnel’s Health and Wellbeing (I-BEST): 3646 teachers from France, 2349 from Québec, 1268 from Belgium, 302 from Morocco, 222 from The Gambia, and 215 from Mexico. For each country/territory and each wellbeing indicator, we used a forward stepwise regression procedure to identify important determinants among a carefully selected set of 31 sociodemographic, private, and professional life factors. Aside from healthcare access, the factors most consistently and strongly associated with teacher wellbeing in France, Québec and Belgium (samples whose size were ≥1000) were related to the psychosocial and the organizational dimensions of work, namely: feeling of safety at school, autonomy at work, and the quality of relationships with superiors and quality of relationships with students. In the smaller samples of teachers from the three remaining countries (Morocco, The Gambia and Mexico), exploratory analyses showed that the feeling of safety and autonomy at work were, there too, consistently associated with wellbeing indicators. During the COVID-19 pandemic, the factors most consistently associated with teachers’ wellbeing across countries were related to security and autonomy at work, supporting the importance to consider these aspects in a continuous, structural way at school. Factors associated with teachers’ wellbeing in very different contexts require further cross-cultural study.