The purpose of this research is to explore the process of engagement of actors initiated by the headquarters of a national sport federation during the formulation of its sport policy. The Actor-Network Theory and its four phases (problematisation, incentive, enrolment and mobilisation of allies) are used to understand the dynamics of actors during the process, with an emphasis on the constitution, expansion and stabilization of the actors’ network. As part of an intervention research within the French Rugby Union over the 2013–2016 period, three series of semi-structured interviews (58) were conducted with both national and regional actors with various statuses. The French case is of interest beyond France because the organisational configuration of the national federations has specific characteristics that are common to different countries: pyramid structure, state intervention (both financial and human) and relationships between volunteers and employees. The results of this study demonstrate that the process of designing a sport policy is not linear. In addition, some elements that are favourable for the engagement of actors are highlighted, such as having a defined scope of the sport policy to be designed and designating key actors regarding the formulation of the sport policy. These actors should be able to act as spokespersons in front of other actors in the network. The innovative methodology used in our research is relevant to policy makers because it helps them engage other actors during a concrete transformation project, namely, the formulation of a policy.