Modern rice varieties are considered the best solution to manage the dilemma of increasingly scarce resources and rising food demands in the developing world. Although rice is widely cultivated in Vietnam, little is known about the factors affecting the farm households’ decision to adopt modern rice varieties and its economic effects across land-size groups. Using the propensity score matching combined with the difference-in-difference (PSM–DID) method, this study examines the effects of the adoption of modern rice varieties in Vietnam. The estimates reveal that the effects are distinguishable among outcomes of interest and farm sizes. In particular, only large landholders significantly improve their productivity by adopting modern varieties, while the effect of adoption on value-added is negligible regarding farm size. The findings suggest that the Vietnamese government should enact relevant policies, especially on land consolidation and land market, to enhance the effectiveness of rice production.