Closely related to justice, this article explores how water governance can be fairer and more effective in the Mekong Region where choices are being made about using and sharing waters that might produce more energy; increase or decrease food production; sustain or threaten livelihoods; and maintain or degrade vital ecosystems and their services, upon which societies depend. Debate and discussion aimed at producing reasonable, well-informed opinion have been in short supply. However, deliberative processes, where inserted into political arenas, are making water governance fairer and more effective, by reducing power imbalances among stakeholders and assisting negotiations to be more transparent and informed. This article presents an agenda for a new frontier in the field of deliberative governance: constructive engagement in water governance arenas through the promotion of inclusive, deliberative processes that emphasise different perspectives, critical analysis, learning and institution-building whilst respecting rights, accounting for risks, acknowledging responsibilities and fairly distributing rewards. This agenda is inspired by promising examples, from the Mekong Region and elsewhere, which demonstrate the need for deliberation that is information-rich, flexibly facilitated and actively promotes analysis of different views. The deliberative water governance agenda should be attractive to proponents of fairness, effectiveness and social justice in water governance arenas and their consequent decisions and impacts.