After considering significant literature on sustainable supply chain management (SSCM), it is evident that research has neglected the social dimension and still lacks in highlighting the role of sourcing intermediaries in supply chains. The apparel supply chain has increased enormously in length and complexity, driving apparel retailers to employ sourcing intermediaries who manage their sourcing activities with suppliers from developing countries overseas. Thus, the purpose of this study is to enrich existing findings on SSCM by exploring the management of social sustainability when sourcing intermediaries are in between the focal company and the respective developing country factories. More specifically, this study aims to understand the role of apparel sourcing intermediaries for the implementation of social management strategies based on the perception of multiple supply chain actors. Qualitative data was collected through semi-structured interviews conducted in Vietnam and Europe. Ultimately ten propositions are presented, all explicitly concentrating on the apparel intermediary’s role as a significant enabler for social sustainability in apparel supply chains. The roles are social sustainability, supplier developer and coordinator, gatekeeper and safeguard, cultural broker, and social risk manager. The social sustainability roles assumed by the apparel sourcing intermediary offer great opportunities to both apparel retailers and developing country factories.