Multipartner alliances (MPA, i.e. alliance with more than two partners) dedicated to innovation have multiplied in the last decades. Their specificities raise important managerial questions. Among them, concrete interactions and relations between partners are not well understood. Yet they are essential to understand these organisational arrangements and to win the innovation race of our time. That is why we study the relational practices taking place in MPA. We claim that the framework of relational practices identified for dyadic alliances (Ness, 2009) is insufficient and suggest a complete framework of relational practice in MPA to fill this gap. We elaborated this framework drawing on a broad range of literature and by inferring relational practices from case studies. Our theoretical proposition is that beside integrative and distributive relational practices (i.e. consisting mainly in value creation or value capture), a third relational practice is implemented that is specifically appropriate to MPA. We thus name it Multipartner relational practice. This relational practice consists of three governance mechanisms: community, interpreneurship and sub-groups; and one negotiation strategy: consensus reaching. The two cases we study and compare are MPA dedicated to additive manufacturing national strategies in France and the UK. They can be more precisely named National Technology MPA. These cases allow us to theorize from contemporary empirical contexts. They are also appropriate for comparison because they take place in similar contexts. Our observations show that both National Technology MPA are evolving through different phases (that can be differentiated by their aims even if they overlap) using common relational practice. During an initiation phase, the creation of the MPA, the interactions rely on a community and interpreneurship based governance with a problem solving negotiation strategy. Later, during the operation phase, when strategizing is an important task, the MPA is governed by sub-group and interpreneurship governance, with a consensus based negotiation. When the times comes for implementation– at the outcome phase – actors implement a sub-group and price based governance mechanism. Common observations between the two cases tend to support our framework and reveal patterns of evolution of relational practices in MPA. However, theoretical generalization remains limited to a relatively narrow range of contexts and our research should be deepened with other case studies. Our results contribute to fill the gap of relational practices taking place in MPA and their evolution. Our study is also embedded in the context of innovation policy. If it is not the focus of this paper, the research could also bring insights to this literature.