This paper argues that coastal development in Vietnam and market‐based economic reform, more broadly, have produced household vulnerability in the form of food security for elderly residents left behind by rural–urban migration. Elderly only households are growing in proportion in rural Vietnam as the number of elderly individuals and rates of out‐migration increase. In Đông Hải, a small, shrimp‐farming village in the Mekong Delta, the livelihood transition to intensive shrimp aquaculture and resultant rising debt has pushed young adults out of the community in search of wage labor to support their families, leaving their aging parents behind. With that important loss of social capital, the subsistence strategies of elderly only households are constrained and food insecurity results, as evidenced in this study by dietary diversity and reliance on diet‐related coping strategies.