Irrigation is one of the most critical factors contributing to Vietnam's agricultural sector's overall success and rice production in particular. The rice area in Vietnam with irrigation works that can actively control irrigation and drainage is 89,46% and 86,37%, respectively. Some rice land has not been actively irrigated and drained, affecting farmers' rice production. Besides, irrigation works are damaged due to time and natural disasters. Therefore, the Vietnamese government built new irrigation works and improved old irrigation facilities to ensure the water supply for production and daily life. This study estimates the effects of irrigation system improvement on the rice productivity and per capita income of farmers in Vietnam. The difference in difference (DID) method with the panel data from the Viet Nam Access to Resources Household Survey (VARHS) in 2016 and 2018 is utilized in this paper. The results show that improvement of the irrigation system contributes to an increase in the rice productivity of the farmers by about 4,5%. Moreover, improving the irrigation system significantly affects per capita income, increasing by nearly 115%. Our results indicate that improving the irrigation system is essential to increasing rice productivity and farmers' income.