In developing countries where agricultural production is exposed to adverse impacts of climate change, out-migration is commonly perceived as a safety net for poor farmers who lack adequate access to resources and capacity to adapt to change. In the Vietnamese Mekong Delta (VMD), the land use change driven by the state-led development of water engineering systems (e.g., dykes) and subsequent agricultural mechanisation processes, while it fosters intensive agriculture-oriented development policies, is perceived as the key factor that dispossesses livelihood opportunities of a large segment of rural societies, particularly the poor. This paper aims to examine how land use change is linked to farmers’ decisions to migrate. Drawing on the mixed data gathered from focus group discussions, in-depth interviews and household surveys in three flood-prone communities in the VMD, the paper argues that the land use change forms an underlying driver for the surge of out-migration of the rural poor. The study findings indicate that the dyke development for rice-based agricultural modernisation process (e.g., widespread adoption of agricultural mechanisation) creates greater risks of unemployment borne by the poor. As such, they exert out-migration as a viable strategy to adapt to change and to avoid “locked-in” impoverishment in rural areas. This study advocates that policy considerations for delta’s rural development should be grounded on the empirical understanding of the land use change and its significance to ensure rural societies’ gaining equal access to employment. The study findings provide opportunities for further investigation in comparison with other case studies across the Mekong region and beyond, where state governments still play a dominant decision-making in agricultural development.