The aim of the present study was to investigate the relationships between teachers' personal (i.e. psychological capital, social support, ICT skills), job-related factors (i.e. school principal's transformational leadership), their emotional well-being (i.e. positive and negative affect), and their job performance (i.e. task performance and teaching quality) during remote teaching due to the COVID-19 pandemic. The study was conducted in Spring 2020 on a sample of 1655 Croatian teachers. The results of the structural equation modelling (SEM) showed that teachers' positive affect partially mediated the relationship between all examined factors and teacher performance. Teachers who rated their social support, psychological capital, and ICT skills as higher, as well as those who perceived greater transformational leadership of their school principals, also experienced positive affective experience to a greater extent, which, in turn, was positively related to self-reported task performance and teaching quality. However, a mediating effect of negative affect in the relationship between examined factors and job performance was not found. Our results contribute to the understanding of factors that are related to teachers' emotional well-being and job performance, during challenging situations, such as the COVID-19 pandemic.