This thesis addresses the issue of coordination within the field of mental health in Belgium. More specifically, it focuses on the arrival of coordination professionals in a context of mandated networking of local actors following the formulation of several policy plans, aimed at addressing the negative effects of the increasing fragmentation that the sector has experienced for several decades. The author proposes to analyse the emergence of these new workers, called “network coordinators”, from four perspectives – instruments, practices, knowledge and experience – in an attempt to understand what coordination work consists of and how it takes shape within the field. Deploying a qualitative methodology based mainly on a series of observations of coordination work and interviews with coordinators and other field actors, this thesis highlights the central role of these new coordination professionals in the implementation of these policies at local level. The author proposes an analysis of the daily work of network coordinators and, in so doing, of the complex context in which it takes place and the difficulties they encounter. By describing the contours of a promising but unachievable mandate, this thesis provides an understanding of the disillusionment that some network coordinators experience with their new role. Finally, this work takes a critical look at these coordination initiatives by showing both the rareness of the profile of the “successful coordinator” – who is no more than a pragmatic coordinator with multiple skills and knowledge – and more broadly, by highlighting the limits of the network model as it is currently conceived and implemented.