The Vietnamese Mekong Delta (VMD) is currently grappling with multiple water challenges. These challenges stem from the alteration of the Mekong River’s natural flows caused by upstream hydropower development, unpredictable rainfall patterns, and local policies that prioritize agricultural production. This article examines how these combined stressors have prompted a shift in water management strategies—from focusing on water expulsion to water retention—to tackle water scarcity and achieve long-term water security in the VMD. Case studies from An Giang and Ben Tre showcase evolving water management approaches, revealing how state-led expansions of water infrastructure have contributed to water scarcity and increased the vulnerability of rural inhabitants. Achieving sustainable water security requires integrating empirical research with policy insights by considering the complex dynamics of local and transboundary water conditions, as well as the contestations between state-driven water management strategies and livelihood preferences of local farmers. We advocate for a balanced approach that recognizes and utilizes diverse water resources for rural livelihood development, particularly in coastal zones. While freshwater remains essential for agriculture and household needs, incorporating brackish and saline water into local development strategies can better align with farmers’ aspirations for sustainable and profitable livelihoods.