Buying firms must pay increased attention to supply chain sustainability issues, as stakeholders might hold them responsible for non-sustainable supply chain activities. Frequently, sustainability problems occur upstream at the sub-supplier level. Building on the literature on multi-tier supply chains (MSCs), we investigated the sustainability management strategies of buying firms in the food, apparel, packaging, and consumer electronics with regard to second-tier suppliers and beyond. In particular, we analyzed seven cases of global MSCs and found four different characteristic MSC types-open, closed, third party, and "don't bother". We identified three main factors-supply chain complexity, the sustainability management capabilities of the first-tier supplier, and the type of sustainability in focus (i.e., environmental or social sustainability)-that determine when and how buying firms actually extend their sustainability strategies to their sub-suppliers.