Seawater intrusion (SWI) threatens groundwater quality in coastal aquifers in many regions all over the world. The aim of this study is to understand the state of the Quaternary aquifer in the Sudr area, South Sinai, Egypt, and to assess the groundwater quality for irrigation using hydrochemical indicators and GIS. 60 groundwater samples were collected from the area and physical and chemical parameters were determined. The high salinity values are in the West and North-West, while the values decrease towards the east near the main Wadi channel. The Piper plot suggests that the main water types in the study area are Na-Cl, Ca-Cl, and Ca-Mg-Cl. As per the US Salinity Diagram (USSL) and Doneen's diagram, most of the groundwater samples are applicable for plant species with high salt tolerance. These confirmed by SAR, Na%, PI, PS, KI, MH. The findings of Residual Sodium Carbonate (RSC) suggest that all groundwater samples are deemed safe for irrigation. This study helps to monitor groundwater quality in coastal aquifers which might be a useful tool for policymakers and stakeholders.