State and non-state actors increasingly work across scales to address complex environmental problems. Prior studies of stakeholder participation have not fully examined how collaborative processes play out in multi-level policymaking. At the same time, multi-level governance studies do not adequately investigate the impacts of stakeholder participation. This study examines the cross-level interactions of influence and information in the participatory implementation of the European Union's Water Framework Directive. This directive is an example of mandated participatory planning, a relatively new approach that engages grassroots collaboration through a top-down structure with nested policy cycles. A case analysis of three collaborative planning units in the Land of Lower Saxony, within the federal governance structure of Germany, finds limited influence and information transmission across levels via formal planning and implementation processes. However, the collaborative efforts did yield alternative pathways for achieving substantive progress toward the directive's aims via learning, coordination, and buy-in among participants.