Purpose: The well-being of individuals is an essential issue of sustainability research. This study aims to focus on the particular case of teleworkers and the work conditions which may hinder their well-being. More specifically, this study analyses the impact of social isolation and work overload on the work engagement and life satisfaction of teleworkers during COVID-19 pandemic. Design/methodology/approach: With a sample of 188 workers from the Portuguese banking sector, the authors use structural equations modelling to test a conceptual model. The authors carry out data analysis with partial least squares. Findings: Social isolation and work overload are both negatively associated with the three dimensions of work engagement, namely, vigour, absorption and dedication. In turn, vigour is positively associated with life satisfaction. Social isolation and work overload are indirectly associated with life satisfaction through vigour. Results from multi-group analysis show that the negative relationship between social isolation and dedication is stronger for less senior teleworkers. By contrast, the negative relationship between work overload and dedication is stronger for more senior teleworkers. Additionally, the positive relationship between vigour and life satisfaction is stronger for permanent workers than for temporary ones. Originality/value: This study tests the assumptions of the job demands-resources under the novel conditions of telework during COVID-19, focusing its ubiquitous conditions -- social isolation and work overload. For human resources managers, this study highlights the need to take seniority and job stability in consideration when devising onboarding and working arrangement strategies for teleworkers.