The imperative for vulnerable populations to adapt to greater environmental variability is increasing in lockstep with the onset of wide-ranging climate change impacts. However, while critical adaptation research emphasizes the necessity of addressing the underlying drivers of vulnerability to climate change, mainstream approaches to adaptation stress economic growth as a prerequisite for climate responses. Accordingly, capital-intensive adaptation measures promote competitiveness to spur economic growth in the Vietnamese Mekong Delta, where more than 18 million people face environmental hazards such as seawater intrusion, flood, drought and cyclones. This study evaluates competitiveness as a mandate for effective climate change adaptation. It finds that adaptation can advance either competition or vulnerability reduction, but it cannot logically or pragmatically pursue both.The author thanks the anonymous referees for their helpful comments as well as Daniel Esser, Jamey Essex, and the participants of the Research-in-Progress Series workshop hosted by the Development Geographies Specialty Group of the American Association of Geographers and the German Development Institute (Deutsches Institut für Entwicklungspolitik) in January 2021. This workshop yielded insightful questions and comments that were invaluable to the development of the article. Field research for the study was made possible by grants from the Council of American Overseas Research Centers and the Institute of Human Geography, to which the author is indebted for their support.