Collaborative approaches are increasingly used to address challenging environmental problems in the United States and around the world. The inclusion of multiple stakeholders and sources of information is expected to solve such problems. Prior research has highlighted the importance of collaborative process characteristics in reaching agreements and building social capital, but less is known about what factors affect the implementation of such agreements. A parallel stream of research in policy implementation theory has developed variables and frameworks to explain the implementation of authoritative policy prescriptions. Drawing on the top-down/bottom-up perspectives on implementation, this study examines implementation of collaborative recommendations along a continuum of top-down/bottom-up approaches. A comparison of six cases in two states (Lower Saxony, Germany and Ohio, United States) indicates important differences in perceptions of implementation and environmental improvements, although whether an effort was more top down or more bottom up was not a key determinant of results. In both states, stakeholder collaborative planning efforts included substantial involvement from stakeholders and multiple government agencies and levels. Participants in the Ohio cases perceived higher levels of implementation and environmental improvements. Key factors promoting implementation of plan recommendations were resources (funding and a full-time coordinator), willing land owners, and networks. In the Lower Saxony cases, collaborative plans were seen as less impactful, but nevertheless the process of plan development did foster networks for implementing some actions to improve water quality.