Nonpoint source pollution from agriculture represents a major threat to the quality of water in the European Union (EU) context. As part of the implementation process of the EU Water Framework Directive in France, the cooperation between water suppliers and agricultural stakeholders has been recently promoted for limiting diffuse agricultural pollution at the water catchment level. Based on a conceptual framework combining transaction cost economics and the social-ecological system (SES) framework, we identify the conditions under which such collective action is effective for the restoration/maintenance of water quality. The research relies on a cross-case comparison of cooperation in six drinking water catchments. A qualitative analysis of primary data collected at the national, water basin and local levels serves as a basis for the multi-case investigation. Variables related to the hydrogeological system, the stakeholders involved, the contracts governing cooperation and the economic and policy contexts are shown to interact in their influence on collective action. The results highlight the importance of the match between contract incentives and the characteristics of the local context and the potential complementarities between informational, regulatory and economic policy tools for enhancing the effectiveness of collective action for water pollution control.