As supply chains have become an important source of corporate competitiveness, firms face new challenges in integrating environmental and social themes to reduce risks arising in the supply chain and enhance overall supply chain effectiveness. This study utilized the concept of sustainable supply chain management, which integrates sustainability themes with supply chain management, to present an integrated model of transaction fairness, eco-friendliness, and social responsibility in the supply chain—dimensions that had previously been addressed individually and partially. Employing social capital theory, which is importantly utilized in supply chain research, the study proposed a theoretical model examining how sustainable supply chain management affects supply chain environmental performance and production-operations performance, and conducted empirical analysis. A structural equation model was analyzed using survey data from small and medium-sized suppliers in Korea. The research results confirmed that sustainable supply chain management contributes to the formation of relational capital between buying firms and supplying firms, and ultimately improves environmental performance and production-operations performance. Among the constituent factors of sustainable supply chain management, transaction fairness had the greatest impact on relational capital formation and performance improvement. This study emphasizes that transaction fairness, eco-friendliness, and social responsibility in supply chain management share very similar characteristics and therefore should be addressed in an integrated manner. Furthermore, it provides implications for managers of all participating firms in the supply chain that sustainable supply chain management should be recognized not as mere benevolence by large firms or as entitlements that small and medium-sized suppliers should naturally receive, but as strategic activities necessary for strengthening social capital and improving competitiveness in the supply chain.