Employing a sample of 126 suppliers in Korean electronic industry, this research examined the effects of institutional environment, social capital and strategic importance in manufacturer-supplier relationships on knowledge sharing. Building on the relational view and knowledge-based theories, this study proposed that these factors facilitate knowledge sharing in manufacturer-supplier relationships and that knowledge mediates satisfaction between manufacturer-supplier relationships for competitive advantage. Results indicate that institutional environment, social capital and strategic importance in manufacturer-supplier relationships are indeed associated with greater knowledge sharing. Inter-firm satisfaction is, in turn, positively associated with knowledge sharing for competitive advantage through technical support, financial support, competence increasing. Further, results provide evidence that knowledge sharing plays a mediating role between institutional environment, social capital, strategic importance and inter-firm satisfaction.