The concept of social innovation has received considerable interest in recent years, both in research and policy. One of the main challenges lies in understanding how to move from experimentation to spreading social innovation and bringing it to widespread use. This is how concrete objectives for sustainable development can be achieved in a given territory. Intermediation plays an essential but little-studied role in the spread of social innovation. In this study, we endeavoured to understand how the social innovation intermediation process is constructed and its effects. We interconnected the actor-network theory and middleground approach to separate the practices and dynamics at work in an emblematic case: the Start-Up de Territoire (in France). By entering the 'black box' of the social innovation factory, we observed how the role of social innovation intermediary is built gradually over time. We then identified three main social innovation intermediation processes that condition its scale-up: building the vision of the territory, expanding the network, and defining how the different levels interrelate by distinguishing between top-down and bottom-up translations.

Our analysis contributes to the literature on social innovation by providing an interpretative framework to understand how intermediation dynamics interrelate at different levels. This contribution thus makes it possible to strengthen the theoretical foundation of social innovation and explore the connection between social innovation and transformation.