This study links theories of relationality and institutional change to deepen understanding of professionals’ role in globalization. In previous institutional research, it has been conventional to treat professionals as agents of firms or transnational organizations, and institutional change as the result of planned, strategic ‘professional projects’. By bringing a relational analysis to bear on the problem of institutional change, this study reasserts the theoretical significance of individual agency and everyday interactions between professionals and their clients, peers, and organizational environment. It also broadens the model of agency to include invention and improvisation by individual professionals, as a counterpart to collective strategic action. The argument is based on data from a 16-nation study exploring the emergence of a particular ‘globalized localism’: the transformation of the asset-holding trust from a tool of medieval English landowners into a mainstay of contemporary international finance. Drawing on interviews with 61 wealth management professionals in Europe, Asia, Africa, and the Americas, this article uses their accounts of the diffusion and deployment of trusts to specify a new, more detailed model of the ways local practices and ideas develop into global institutions