The fashion industry‘s linear system of take-make-use dispose creates large negative socio-environmental impacts and economic value losses. In order to tackle global sustainability challenges and ensure long-term viability, this industry is facing a need for circularity and closed-loop approaches. This thesis explores how fashion designers can aid the transition towards a circular economy (CE) in the fashion industry, investigating (a) new requirements, tasks and interactions fashion designers may face within their organisation, (b) the designers‘ potential new role(s) in the transition process and (c) which systemic factors may influence designers in the transition towards the CE. For this purpose, 15 interviews with ten fashion designers working in medium and large fashion companies and five key informants (circular economy and circular fashion expert, design researcher, product developer, product manager and sustainability manager) were conducted. The results are summarized in a theoretical model (ORFDCE model (Organisational Roles of Fashion Designers for Circular Economy)) and suggest that designers can take up three central roles in the transition process, provided that they expand their sustainabilityrelated knowledge and are supported by four central systemic organisational changes. This thesis outlines the intersections and connections between the theoretical concepts of organisational roles, power, design management and systems thinking, creating a novel systemic understanding in the context of the CE and expanding the existing research in this field. The developed model enables medium and large sized fashion companies on their way to circularity to identify their specific standing in the transition process and develop designer training and support measures aimed at realizing their designers‘ full potential.