PurposeThe objective of this research is to examine the mediating role of employees' well-being in the workplace in the relationship between the dimensions of social capital, namely structural, relational and cognitive social capital and knowledge sharing, as well as the moderating role of enterprise social networks between knowledge sharing and employees' well-being.Design/methodology/approachA quantitative approach was performed within a sample of 168 middle managers working in knowledge-intensive firms in Tunisia. The Partial Least Squares method was used to analyze the data collected.FindingsResults highlight the importance of the dimensions of social capital as a lever for boosting knowledge sharing. It also reveals that employees' well-being plays a mediating role in the link between structural and relational social capital and knowledge sharing. Moreover, findings show that while enterprise social networks use does not moderate the relationship between employees' well-being and knowledge sharing, it has a positive and significant effect on knowledge sharing.Originality/valueOn the basis of a socio-technical perspective of knowledge management, this research pioneers the examination of the mediating effect of employees' well-being in the link between dimensions of social capital and knowledge sharing and the moderating role of enterprise social networks use within knowledge-intensive firms. Findings of this study may help managers of knowledge-intensive firms in boosting knowledge sharing within organizations, in improving knowledge workers' well-being and thus in motivating and retaining these talented employees.