Groundwater is widely used for domestic, agricultural, and industrial purposes in the Vientiane basin. The trend of groundwater use is increasing but the usage of the mentioned groundwater is without proper study and monitoring. Six climatic scenarios from three General Circulation Models (GCMs) under Representative Concentration Pathways (RCPs) 4.5 and 8.5 were used to project rainfall and temperature in the future (2021–2050) periods. The numerical models HELP3, MODFLOW, and MT3D were used for groundwater recharge estimation, groundwater potential, and salinity distribution, respectively. The study found that during the following 30 years (2050), rainfall is expected to rise by 16, 17.52, and 49.93% for the MPI-ESM-MR, MIROC5, and CNRM-CM5 (under RCPs 4.5 and 8.5), respectively. Groundwater recharge is estimated to rise from baseline throughout all future climate conditions. Climate change's impact on salinity distribution in depth aquifers, the area with the water with the TDS between 500 and 1,500 mg/l will tend to decrease, whereas the freshwater (TDS <500 mg/l) area will tend to increase. Annual groundwater replenishment is expected to increase from current levels in all future climate scenarios in the range of 334–401 MCM/year or approximately 22.7–47.5%.