Changes in political, social and environmental arenas increase challenges for complex policy processes. However, areas of public policy are dominated by anachronistic instruments. These are potentially unsuitable and unsustainable due to their failure to account for geopolitics or entertain alternative, potentially more appropriate, policies and approaches. This can become evident in a certain discourse or narrative continuously dominating an area of governance and decision making, even when they conflict with contemporary needs and the geopolitical contexts. This appears prevalent within water management, particularly in the transboundary context. Here, outdated paradigms dominate the agenda, despite geopolitical changes, resulting unsustainable outcomes. The concept of “discourse inertia” is developed to better understand these situations. Discourse inertia is considered and demonstrated in the context of transboundary water in the developing economies of South and Southeast Asia. This contributes to understanding how an actor group can maintain dominance and the wider implications of such situations.