This study assesses the quality of domestic ground water sources close to petrol filling stations with a view to determining the level of vulnerability. It Map out filling stations and domestic water sources within their proximity with the aid of GIS, determining their level of proximity to domestic water sources, carrying out physiochemical analysis of the water samples within the proximity of filling station within the study area to check the level of contamination. Primary and secondary data sources were used, coordinates point of filling stations and identified ground water source were captured and referenced on digital map of Minna, Buffer width of 50meters were performed to ascertain the vulnerable ground water source. Eight (8) ground water sampled were collected within 50meters to petrol filling stations and Two (2) were collected above 50 meters. The ground water sampled were subjected to five major physicochemical parameters; Ph, Conductivity, Temperature, Total Dissolved Solid and Total Petroleum Hydrocarbons. The findings show that thirty (30) different ground waters sources were identified within the proximity of less than 50meters in the area and discovered that well 3 has the highest concentration of conductivity with 1364 followed by well 2 with 1025. The study discovered that Total Petroleum Hydrocarbon (TPH) is present in all the sampled well expect for the two (2) sampled well that were above 50meters proximity to the petroleum filling stations which is an evidence of contamination of underground water due to operation of petroleum filling stations in the study area. The study thereby recommends that distance between the wells and petroleum filling stations had an influence on the concentration of TPH, therefore it is suggested that wells should be cited far away from filling station so as to reduce the amount of TPH that may get into the underground water sources.