The article focuses on elucidating the transformation of rice production in South Vietnam from 1965 to prior to April 30, 1975, under the impact of the introduction of high-yielding rice varieties and a set of policies promulgated and implemented by the Government of the Republic of Vietnam. Employing the historical method in combination with qualitative analysis, the article argues that, prior to 1965, rice cultivation relied predominantly on local varieties; thereafter, high-yielding rice varieties were introduced as a key technical solution. These new varieties featured short growth durations, enabling multiple cropping within a year, strong responsiveness to fertilizers, and wide adaptability. Consequently, they facilitated a shift toward intensive multi-cropping systems, the expansion of irrigation infrastructure, mechanization, and the increased use of modern agricultural inputs. As a result, rice yields and total output rose substantially, helping to reduce dependence on rice imports and improve farmers’ livelihoods in many regions. However, the benefits were uneven due to disparities in irrigation conditions and access to agricultural inputs. Moreover, new challenges emerged, including high production costs, pest outbreaks, grain quality issues that did not fully meet market preferences, and environmental risks. The study concludes that high-yielding rice varieties constituted a key driving force behind the intensification and partial modernization of rice agriculture in South Vietnam prior to 1975.