The aim of this article is to provide an understanding of how the supplier selection process used by buying organisations to establish socially sustainable supply chains has evolved from the traditional purchasing function. Through the application of a socially responsible purchasing (SRP) approach, organisations are attempting to address the challenges of selecting appropriate suppliers to engage with. To achieve SRP, behavioural agency attributes were found to complement traditional agency forms of governance from the start of the process. Through the use of an exploratory case study approach, three focal (purchasing) firms pursuing a strong sustainability agenda, and two supply chain intermediary organisations were investigated. The results show that supplier development activities previously positioned post-selection are now performed at the pre-selection stage, moving them to the beginning of the process. Suppliers must now demonstrate commitment to sustainability through implementing improvements highlighted in corrective action reports at the pre-selection point before any financial transactions occur. The movement of post-selection supplier development activities to the pre-selection stage, to align sustainability goals and reduce risk, is a significant finding of this article that purchasing personnel and suppliers should consider in the establishment of a socially sustainable supply chain.