In recent years, interest has grown in collaboration in public policy. Responding to the complex issues now playing out in cities, scholars are focusing on localized governance relations that blur boundaries between public, private, and community sectors. This article introduces discursive localism as a framework to understand better collaborative urban governance. It argues that ideas play a pivotal role in motivating collective action, channeling policy resources, and shaping governance relations. Although recent urban-focused accounts of collective action suggest a role for ideas, systematic attention to their normative-philosophical and cognitive-programmatic dimensions reveals how different policy discourses frame incentives and institutions for collaboration. Applying discursive localism to Toronto, Canada, the article describes change processes across three complex policy fields. Governance arrangements are argued to flow from the operative policy discourses, especially whether their normative and cognitive dimensions are integrated, dissociated, or fragmented.