How might service design realize change in legacy organizations? This chapter discusses this question by linking service design research with literature on legacy organizations, which are characterized by highly regulated and well-established constellations of actors, resources and structures. Illustrative examples of service design approaches from healthcare and legal services show that tapping into agency at the individual level is important to enable and drive collective change. In this context, the role of service design is to establish an open and safe environment for actors to unpack underlying assumptions and experiment with new ways of working that can catalyze larger-scale change.