The important role of local governments for the dynamism of entrepreneurial ecosystems is a recognized fact. Our study focuses on the role of municipal leadership and public institutions in the development and maintenance of vibrant entrepreneurial ecosystems, while taking into account local characteristics. Three entrepreneurial ecosystems are studied: the cities of Shawinigan, Trois-Rivières and Sherbrooke, in the province of Québec. We gathered our data through surveys, interviews and observations. Our results show that clear, assertive and concerted municipal leadership stimulates the desire to transform and fuels the cultural change sometimes required within ecosystems. Municipalities play a unifying role between the different actors of the ecosystem. They are the guardians of a balance point between centralization and decentralization: a mutualization that is articulated around the will for collaboration between actors, the need for optimization of resources and the existence of unifying projects.