The coastal sedimentary transboundary aquifer of west Africa is partly shared by three countries including Benin Republic, Nigeria and Togo. The groundwater resources in the area are mainly for domestic water supply in both urban and rural areas. However, with the pressure on groundwater some problems exist which include but not limited to overexploitation, contamination and pollution from poor waste disposal and intrusion of sea water. The present work entails the identification of aquifers, determination of the quality status of the groundwater and assessment of the coastal aquifer vulnerability to pollution. The results showed that within the coastal area, seven (7) aquifers were identified as follows: Lower and Upper aquifers (Benin Republic), Deltaic and Benin Aquifers (Nigeria) and Continental Terminal (CT), Eo-Paleocene (Eo-Pa) and Maestrichtian (Ma) aquifers in Togo. The average physicochemical compositions are generally within the levels of portability. The mean concentration of nitrate however, exceeded 10mg/l in all the aquifers except the Deltaic Aquifer (mean 2.82mg/l) in Nigeria and Eo-Pa Aquifer in Togo (mean 7.88mg/l). The major factors controlling the water chemistry in the study area are sea water intrusion (enhanced Cl), carbonate dissolution/weathering (enhanced concentration of Ca & HCO3) and human activities (enhanced concentration of NO3). Vulnerability assessment according to GOD method indicates that the aquifer systems are lowly (Upper, Eo-Pa & Ma aquifers) through moderately (Deltaic Aquifer & CT aquifers) to highly (Lower & Benin Aquifers) vulnerable. Management of the groundwater resource will include mainly legislation towards construction and use of shallow wells/boreholes and regulation of abstraction to reduce saline contamination and proper waste management ate to reduce the concentration of nitrate as is presently done in Nigeria.