Tacit knowledge is internal to an individual in the form of know-how, experience or expertise. To create and maintain a sustainable competitive advantage, many companies have made substantial efforts to promote employees' sharing of their tacit knowledge. In practice, however, tacit knowledge sharing (TKS) between employees is rare. This study empirically analyses the impacts of individual motivations and social capital on employees' TKS in order to deepen and widen the understanding about the antecedents to employees' TKS. Data collected from 713 employees in multiple industries were empirically tested by using structural equation modelling analysis through partial least squares. The analysis results show that anticipated intrinsic rewards and social capital positively influence employees' TKS whereas anticipated extrinsic rewards have a negative effect on it. Furthermore, they show that employees' attitudes, intentions and subjective norms of TKS play significant roles in linking the effects of individual motivations and social capital to employees' TKS through a combination of expectancy theory and social capital theory based on the theory of planned behaviour. Theoretical and practical implications are presented on the basis of the major findings from this study.