While the concept of an ecological transition is still being defined through an ambiguous process, it also becomes an increasingly urgent municipal governance issue. In places where this governance is multiscalar and the responsibilities are shared among a number of jurisdictions, the absence of a stable and operational definition of a transition adds to the challenge of defining and implementing effective interventions. This paper presents the results of a partnership research with the borough of Rosemont–La Petite-Patrie, in Montreal, that aimed at tackling two questions : “what is an ecological transition at an inframunicipal level ?” and “how can it be implemented ?” The analysis of our partner’s documents and interventions led to the creation of two typologies. The first typology classifies the topics with the concept of ecological transition, while the second identifies the policy instruments used to act on these topics. The results led us to identify three challenges related to the inframunicipal governance of ecological transition : conciliating the living environment-focused approach of the borough and the principles of a just transition, finding new levers for shared responsibility issues, and applying incitative tools and planning regulations (discretionary and/or regulatory) more thoroughly.