​Sustainability advanced to an omnipresent topic among academics and business leaders, while at the same time, a growing share of a firm's total expenditure accounts for purchased products and materials. Even though suppliers become increasingly important for their buyers with regards to sustainability, academic research still lacks a detailed understanding of how sustainability considerations affect the relationship between buyers and suppliers. Thomas Leppelt contributes to extant sustainability literature across the research disciplines of supply chain management, management and marketing by cross-functionally investigating the effects of sustainability on supplier-buyer relationships from both a supplier and a buyer perspective. The results of in total three academic articles provide valuable insights on how buyers as well as suppliers deal with sustainability upstream and downstream the supply chain. The results indicate that sustainability leaders, in contrast to sustainability followers, intensively invest in sustainable supplier relationship management practices. Moreover, a became evident that the effective marketing of sustainability-related capabilities enhances a supplier's reputation and can render comparative advantages, if it sends consistent positive signals to the market and if it integrates purchasing and marketing in the context of sustainability.