The Vietnamese Land Law of 2013 imposed an upper threshold on how much land a farmer may possess. This is a policy that has been found to constrain agricultural development in other countries. Although this restriction of land accumulation is now under review among policy decision makers, there is limited empirical evidence to assess the impacts of landholding on land productivity. To evaluate the impacts of land accumulation on both the technical and environmental performances of farms, this study employed latent class stochastic frontier analysis using data gathered through face-to-face interviews rice farmers in two Mekong Delta rice-producing regions: An Giang province and Can Tho city. We then used multiple linear regression and the ordered logit model to estimate impacts of land accumulation on these performances. The results suggest that land accumulation is more common in An Giang than in Can Tho, yet rice farmers were unable to consolidate separate parcels of rice production land to take advantage of economies of scale. We also found that land accumulation was also positively associated with both technical and environmental efficiencies.