Attention to industry structures and value chain relations is a useful complement to the literature on incumbent firm behaviour in sustainability transitions. In this chapter, we are interested in understanding mimetic behaviour between lead and follower firms and explore whether positions and relationships in value chains may influence how and when firms engage in sustainability reorientation. We study this issue through a detailed case study of two large incumbent firms in the Norwegian oil and gas value chain. Through an event-based analysis covering developments over a 15-year period, we outline how the two firms over time developed sustainability strategies and initiatives. The chapter discusses how the relationship between the two firms have influenced sustainability reorientation in different ways and finally, discusses the value of looking at value chains and inter-firm relationships when investigating the role of firms and industries in sustainability transitions.