Salinity intrusion, caused by global sea-level rise, is a major threat to paddy cultivation in the Mekong Delta of Vietnam (MKD). Salinity exposure reduces crop yields, increases soil salinity, and exacerbates fresh water scarcity, resulting in altered land use decisions and decreased paddy farming profitability. This study evaluates the effects of salinity intrusion on paddy yields and planted acreage, using a 21-year district-level panel dataset from the 13 provinces in the MKD. Specifically, we analyze the relationship between current salinity levels and paddy yield, as well as the relationship between lagged salinity levels and the paddy planted area. We examine these relationships across all districts, as well as for salinity-prone and non-salinity-prone districts and by proximity to the coast (20 km, 20-60 km, and 60+ km). The results indicate that salinity intrusion poses a significant challenge to paddy production in salinity-prone and coastal regions. Salinity level significantly and adversely affects paddy yields in salinity-prone and coastal districts. Similarly, high salinity levels in the past five years significantly reduce planted paddy acreage in these same regions. We also find that paddy yields in the MKD peaked in 2015 and have been declining since. The study highlights the regional differences in challenges associated with salinity intrusion in paddy production. Policymakers and agricultural managers need to take a region-specific approach to ensure that interventions are tailored to the specific needs and challenges faced by farmers. This entails supporting intensified paddy production in less salinity-prone areas and facilitating transitions to economically profitable alternatives to paddy in more salinity-prone areas. / Master of Science / Salinity intrusion, resulting from rising sea levels worldwide, poses a significant threat to paddy cultivation in the Lower Mekong Delta, Vietnam (MKD). The increased exposure to salinity adversely affects crop yields, exacerbates soil salinity levels, and contributes to freshwater scarcity. Consequently, this study aims to assess the effects of salinity intrusion on paddy yields and planted acreage in the MKD. By using a 21-year dataset covering thirteen provinces within the MKD, this study examines the relationship between current salinity levels and paddy yield, as well as the association between lagged salinity levels and the planted area of paddy crops. The analysis considers all districts within the region, distinguishing between salinity-prone and non-salinity-prone districts, as well as the proximity to the coast (20 km, 20-60 km, and 60+ km). The findings indicate that salinity intrusion presents a significant challenge to paddy production in both salinity-prone and coastal regions. High salinity levels substantially and adversely affect paddy yields in these districts. Furthermore, elevated salinity levels within the past five years significantly reduce the planted acreage of paddy crops in the same regions. Notably, paddy yields in the MKD reached their peak in 2015 and have been declining since. This study highlights the need for tailored strategies to address the diverse challenges faced by farmers in different regions. Policymakers and agricultural managers must support intensified rice production in areas that are less prone to salinity, while also promoting alternative crops in regions more vulnerable to salinity. By doing so, we can help sustain agricultural productivity and livelihoods in Vietnam's Mekong Delta, even in the face of salinity intrusion.