Collaborative management is thought to enhance policy implementation in urban settings by overcoming governmental fragmentation, creating greater goal consensus, increasing access to resources, and facilitating policy learning. However, empirical studies of this relationship are conspicuously absent, limiting researchers’ ability to predict how collaborative tools will directly and indirectly affect local implementation outcomes. This article investigates the effects of inter- and intralocal collaboration on the implementation of urban sustainability practices, and investigates interaction relationships to test whether two managerial environmental factors—administrative capacity and stakeholder support—influence the effectiveness of collaborative tools. Drawing data from a national survey, the analysis finds evidence that the effectiveness of collaborative tools depends on the policy target, and that administrative capacity and stakeholder support influence the effectiveness of collaboration in policy implementation. These findings have theoretical and practical implications for how public managers utilize collaborative tools in urban sustainability governance.