A focal company’s boundary of accountability for social or environmental misconduct in its supply chain is hard to define. Non-sustainable business practices can occur at all stages in the supply chain: at raw material exploitation, intermediate production, or transportation. And it can occur atany tier of supplier. Thus investigating multi-tier supply chain sustainability is critical. This chapter argues for the relevance of sub-tier suppliers’ supply chains. Included in the discussion is institutionalizing sustainability standards throughout the entire supply chain, and the role of multi-tier analysis. Background on transparency and impact on sub-suppliers, drivers for active sub-supplier management, and critical factors for sub-supplier management are all introduced. Research implications and directions complete this chapter.