This study examines the mediating role of relational social capital in the relationship between psychological contract and knowledge sharing. This study collected data from 145 academicians in Malaysian public universities using questionnaires. Data was analyzed using Structural Equation Modeling. The findings suggest that trust and collaboration fully mediate the relationship between relational psychological contract and knowledge sharing. The study supports the call for more empirical evidence concerning the role of social capital in understanding the relationship between psychological contract and knowledge sharing. This study contributes to the literature by linking psychological contract and knowledge sharing through the lens of social capital.