This chapter focuses on the interaction between conjunctive management and collective action. Collective action has several characteristics that provide a natural ‘fit’ with conjunctive management. These include building trust and ownership to enhance water user’s acceptance of the need for better and more integrated management and resolving conflict and facilitating trade-offs between and across water users. But what are the opportunities and challenges for conjunctive management through collective action? And what types of settings encourage broad based collective action by water users and governments? These questions are addressed through a comparative analysis of specific instances of groundwater governance in Australia, Spain, and the western United States of America. For each case, the diverse policy and institutional settings are explained, and consideration given to the motivators for, and successes of, conjunctive management and collective action. The chapter draws comparisons across the cases to suggest lessons on incentives for conjunctive management, as well as exploring its challenges, before identifying future directions for more effective integrated water management.