Developing the agricultural system has been an urgent issue of the Vietnamese government recently. A wide range of subsiding and restructuring policies have been legislated, such as applying new technologies, agricultural materials, and hybrid seeds to improve the farming productivity of agriculture production. This article examines the outcome of the government agricultural subsidy policies for a drought-and-disease-tolerant maize variety in two north-west provinces of Vietnam. We apply the Difference in Difference (DID) model to analyze data of 255 Vietnamese maize farming households in 2016 and 2017. By combining all assumptions of the DID method, we assess the result by using three statistical estimation methods: (i) without covariates, (ii) with covariates, and (iii) propensity score matching. Our main finding is that maize farmers who received the subsidized seed variety in the two provinces had lower production compared to those who did not by approximately 1.895 tons/ha. The study therefore recommends that the government should consider other types of subsidy such as extension training programs to improve the productivity of the farmers.