This article identifies a set of practices through which multiple actors, from the European Commission to local governments, perform the concept of the metropolitan region. It specifically investigates the practices and actions which brought this concept into being in the Prague metropolitan region of Czechia. We uncover how the meanings associated with the concept of the metropolitan region evolved through material-discursive practices constitutive of regional institutionalization. The article unpacks five practices which lie behind the initial stages of regional institutionalization: advocacy, framing, customization, implementation and evaluation. It contributes to both the conceptualization and practical knowledge of metropolitan development, planning and institutionalization in three ways. First, in suggesting a set of institutionalization practices, it redirects attention towards what actors do. Second, it highlights the role of materiality mutually intertwined with discursive elements. Finally, it documents how the intersection of multiple governance levels provides key actors with the resources needed to engage in the reconceptualization and institutionalization of the metropolitan region.