Our study investigates how firms strategically establish buyer-supplier relationships to enable the transition to Circular Economy (CE) supply chains. Amid increasing pressures from environmental regulations, sustainability goals, and stakeholder expectations, firms face the challenge of sourcing reliable quantities of recycled materials to replace virgin inputs. Our research addresses the question: “How do firms strategically approach the use of recycled materials as production inputs?” We explore whether firms “shape” market conditions through proactive engagement or “adapt” to existing constraints, analyzing the implications of these strategies for advancing CE practices. Employing an inductive, qualitative research design, we examine firms across diverse industries. Data collection includes semi-structured interviews and field observations, focusing on material replacement projects such as transitioning from virgin plastics to recycled inputs. Preliminary findings highlight two distinct approaches: strategic, goal-driven methods that align with corporate sustainability objectives and opportunistic methods arising from emergent opportunities and managerial initiative. These approaches differ in timelines, resource allocation, and project outcomes, offering valuable insights into CE adoption dynamics. Our research contributes to understanding how firms integrate economic, environmental, and social sustainability in supply chain decision-making. By highlighting the interplay between structured strategies and emergent behaviors, we challenge traditional assumptions about CE implementation. Additionally, we provide actionable insights for firms seeking to align their CE efforts with market realities and sustainability goals, offering a framework to navigate the complexities of transitioning to circular and regenerative supply chains.