This chapter explores how Service Design practice offers a valuable way to inspire and guide sustainable fashion retail. Service Design is considered an approach aimed at understanding people and systems, accommodating changes in behaviour on a system level over time. By analysing the work of students on a leading Service Design Masters programme in the UK, this chapter suggests that new Service Designers are already working on a range of emerging areas of interest in the fashion system: material innovation, behavioural change, business model innovation, and technology. They are applying Service Design to the fashion retail system in wide-ranging ways, from shaping behaviour change at the point of purchase, to building services that aid the diffusion of new materials and technology to helping fashion retail actors to identify and exploit intangible assets within the industry. Besides the value that Service Design provides, the findings also suggest considerable barriers to the use of Service Design in fashion retail, including the challenge of obtaining in-depth contextual knowledge and engagement with various players in the complex system. These challenges suggest the importance of dialogue and collaboration between Service Design and Fashion Design, as two seemingly discrete practices to create an interdisciplinary approach to the complex challenge of building a sustainable fashion retail system.