In this paper, we study the way that nascent occupations constructing an occupational mandate invoke not only skills and expertise or a new technology to distinguish themselves from other occupations, but also their values. We studied service design, an emerging occupation whose practitioners aim to understand customers and help organizations develop new or improved services and customer experiences, translate those into feasible solutions, and implement them. Practitioners enacted their values in their daily work activities through a set of material practices, such as shadowing customers or front-line staff, conducting interviews in the service context, or creating "journey maps" of a service user’s experience. The role of values in the construction of an occupational mandate is particularly salient for occupations such as service design, which cannot solely rely on skills and technical expertise as sources of differentiation. We show how service designers differentiated themselves from other competing occupations by highlighting how their values make their work practices unique. Both values and work practices, what service designers call their ethos, were essential to enable service designers to define the proper conduct and modes of thinking characteristic of their occupational mandate.