More than 130 dams have been built and planned in the Mekong River (MR) basin, and the question about dam impacts on the Vietnamese Mekong Delta (VMD) remains unclear. In this study, we examined long-term changes of the riverbeds and saltwater intrusion in the VMD, and linked with long-term changes of the MR discharge and sediment load caused by upstream dams. Additionally, a coupled Telemac-2D and Sisyphe and Mike 11 models were used. The results show significant riverbed incision in the VMD (by -1.1 m in 2014-2017), and such incision would continue until at least 2026 (by -2 m in 2017-2026) because of dam-induced sediment reductions (by -74% in 1980-2015). These changes have increased saltwater intrusion in the VMD by up to 42% between 1998 and 2016, and shifted the intrusion timing earlier by 1-2 months. Unfavorable upstream dam operations may increase saltwater intrusion by up to 64%.