This research investigates the impact of asymmetric supply chain relationships on sustainable product development in fashion and textiles supply chains in the UK. A qualitative, exploratory, case methodology is adopted by focusing on the experiences of 10 fashion suppliers and two high-street fashion retailers. The research found evidence of bothuniformandco-existingasymmetrical relationships between buyers and suppliers and that these exerted a differential impact on sustainable product development and the balance of commercial motivation and sustainability orientation of retailers and suppliers. This research contributes to theory by linking the concepts of asymmetric relationships and sustainable product development processes.Although limited to one country and sector, the findings are of relevance to fashion and textiles suppliers, retailers and researchers, by raising awareness that balancing their relationships and exchanging information more effectively can support implementation of sustainability policies and practice and enhance sustainable business performance.