Vietnam is one of the countries most severely affected by climate change, and the Mekong Delta is a particularly vulnerable area, suffering heavy economic consequences. Although seasonal flooding is a natural phenomenon in the Mekong Delta, over the past decades, flooding has been occurring with increasing frequency and intensity due to causes related to climate change and development infrastructure development. To overcome these challenges, the German International Cooperation (GIZ) cooperated with the Ministry of Construction and Mekong Delta localities to launch a pilot project of a sustainable urban drainage system (SuDS) in Long Xuyen and Rach Gia and Ca Mau in the period 2017–2020. This study, applies the cost-benefit analysis (CBA) method is applied to evaluate the effectiveness and contribute to determining the model’s scalability for projects in Long Xuyen City, An Giang province. With the CBA method, the results show that the benefits of the model outweigh the costs. Moreover, the results show more clearly intangible benefits such as public health educational opportunities to raise awareness about sustainable solutions in urban flooding control.