Study region: The Mauritanian Coastal Basin (MCB), located between the Mauritanides mountain chain and the Atlantic Ocean (14 degrees-21 degrees N, 12 degrees-16 degrees W), encompasses four main aquifer systems: alluvial, Continental Terminal (phreatic and sub-phreatic), and Eocene. This semi-arid region experiences demographic growth and increasing water demand, resulting in overexploitation of groundwater resources facing significant salinization challenges. Study focus: This study elucidates groundwater mineralization and salinization processes using hydrogeochemical and isotopic analyses of 195 water samples collected between 2013 and 2019. We characterized hydrochemical facies, identified dominant geochemical processes through ion ratios and Gibbs diagrams, discriminated salinization mechanisms using bromide tracers and stable isotopes (delta O-1(8), delta H-2), and assessed spatial water quality variability against WHO standards across different aquifer systems. New hydrological insights for the region: Results reveal diverse hydrochemical evolution from Ca-HCO3 freshwaters in deeper aquifers to Na-Cl saline waters in shallow systems. Silicate weathering and carbonate dissolution control mineralization, while seawater intrusion affects 16.7 % of samples with evaporative concentration dominating 66.7 % of the sampled groundwaters. Stable isotopes confirm widespread evaporation effects (67.8 % samples with d-excess <5 parts per thousand) and paleoclimatic recharge in deeper systems. The percentage of samples complying with WHO standards decreases from the Eocene aquifer (70 %) to the Continental Terminal groundwater aquifer (19 %), establishing a vulnerability gradient crucial for sustainable water management strategies in coastal sedimentary basins under increasing anthropogenic pressure.