Purpose – This study aims to examine what kind of role social capital plays in the relationship between human capital and career outcomes, with a particular focus on testing the mediation and moderation models. Design/methodology/approach – Using data compiled from 111 employees at three financial institutions in Taiwan, social capital was measured by employees based on network in-degree centrality, and development potential was measured by supervisors. Findings – Results showed that the effects of human capital on developmental potential were fully mediated by social capital. Moreover, employees with firm-specific human capital, managerial positions and longer tenure, received higher potential evaluations by their supervisors through their central positions. Research limitations/implications – The study shed light on the direct and significant effects of social capital on developmental potential, while human capital should translate into social capital to get positive career outcomes. That is, it is social capital that transforms human capital into workplace gains, e.g. producing positive career outcomes and increasing supervisors' perception of potential. Practical implications – Employees should make best use of social capital transformed from human capital to obtain positive career outcomes in the organizations. Originality/value – Support for the authors' mediation model suggests that both social capital and careers literature can be enhanced though integration. It follows that future research on career outcomes would benefit from the inclusion of social capital variables.