Institutions are the formal organizations or systems of rules that operate at the city scale. Whether public or private, they play a fundamental role in determining how people access services and experience many aspects of urban life. Unfit institutional structures refer to the instances that hinder just urban sustainability processes and outcomes. This chapter explores two core ways in which institutional structures can result unfit: through the discourse and depoliticization of urban governance, and through the creation and maintenance of institutional silos. Lastly, we highlight policy processes, new municipalism and grassroots acts of social dissensus that can push institutions to be more just and equitable in their pursuit of sustainability.