In recent decades, agrarian transformations in Southeast Asia have resulted in significant environmental and social change, yet insufficient attention has focused on the particular pathways by which these changes have increased vulnerability to climate change. In particular, climate precarity, a situation in which class, social, labour and/or gender inequities amplify negative impacts from climate change, has been on the rise for many smallholders. Using case studies in Vietnam of changes to swidden agriculture in upland areas and the loss of deepwater rice systems in the Mekong Delta lowlands, the paper examines social differentiation and ecological outcomes of these processes and how they have increased climate precarity, particularly for poor households and women. Based on longitudinal fieldwork in affected regions, we identify key changes contributing to climate precarity as farming systems intensify. In particular, loss of flexibility in farmer decision‐making, loss of voluntary engagement with markets, and declining access to social capital and entitlements have increased risks for households and reduced adaptation options. Suggestions are made to more directly address these elements in future agricultural and climate policies, rather than current approaches to climate adaptation that often promote even more intensification of agriculture, which runs the risk of exacerbating precarity.