The Vu Gia Thu Bon (VGTB) River basin is one of the main river basins in Vietnam. The rapid development of dams with deforestation has resulted in many environmental challenges in the VGTB basin, especially floods. Frequent heavy rainfall due to typhoons between September to December causes floods to occur annually. Floods have become an extreme natural disaster in the basin which caused many people and economic loss. For flood mapping, this study aims to apply the Rainfall-Runoff–Inundation (RRI) model in the VGTB River basin. The first-hand setup for two flood events (2017 and 2020) shows a potential result. A flood hazard map can be continually developed using the RRI model in the VGTB river basin.