Aging of groundwater (residence times) is important for estimating groundwater renewability and optimal management of the groundwater resources. The study area suffers from lack of information about the age of groundwater resources. How can integrated environmental isotopes and hydrochemical analysis be used to assess the renewability of coastal groundwater under the influence of water scarcity and increasing salinity in arid and semi-arid regions. So, the aim of this study is to estimate the renewability of the groundwater resources of the coastal aquifer based on environmental isotopes and hydrochemical analytical approaches for 25 and 80 water samples respectively. Hydrochemistry of the groundwater and the spatial patterns of the isotopes for Deuterium (2H), Oxygen-18, (18O), Tritium (3H), Carbon-13 (13C), and Carbon-14 (14C) were analysed to obtain information about the climatic conditions the groundwater resources that exist today were formed and whether effective groundwater recharge is still taking place today. The corrected radiocarbon ages (14C) show young groundwater formed in the Holocene. This result is supported by the deuterium and oxygen-18, which show a relatively heavy isotopic signature and plot close to the global meteoric waterline. This indicates groundwater recharge under warm climatic conditions and excludes paleo-water. Isotopic relationships show that the aquifer receives water from two main sources; direct rainfall with varying degrees of evaporation; surface or mixed water that has undergone significant evaporation prior to recharge. The hydrochemical signature of the groundwaters in the studied coastal area, particularly the Cl/Br ratios, indicate groundwater recharge areas in the mountainous hinterland dominated by basement rocks. The renewable time of the groundwater in the south-western coastal zone of KSA ranges from 1 to 25 years. For sustainable groundwater according to the results, the optimal pumping rate for each well not exceed than 411 m3/day.