There has been an increasing groundwater usage through the abstraction of water from shallow wells without any form of treatment. The effect of using water from a shallow and untreated well is prone to water-borne diseases. This study investigated the groundwater quality of some selected wells in Ogbomoso North Local Government Area (LGA) of Oyo State, Nigeria. One hundred samples were collected for analyses in dry and rainy seasons using Global Positioning System (GPS 72) tools. The sampling points were located based on the existing delineation of ten (10) wards in the LGA, and their nearness to sources of possible pollution such as sewage, waste dump sites, mechanics workshop, cassava processing units, and drainages. These samples were subjected to physical (pH, turbidity), chemical (hardness, chloride, sulphate, zinc, chromium), and bacteriological (coliform and E-coli) examinations by using American Public Health Association (APHA) Standard procedures. The results of the analyses were compared to Nigerian Industrial Standards (NIS) and World Health Organization (WHO) Standards. Statistical analysis was carried out using descriptive (tables and percentages) analyses and inferential Analysis of variance (ANOVA) while a water quality map was developed by interpolating data obtained on a Geographical Information System (GIS) Arc map version 10.0 packages. The results of pH, turbidity, hardness, chloride, sulphate, zinc and chromium values of the samples ranged from 5.8-7.3 mg/l, 5.4-7.3 mg/l; 0-8 NTU, 0-1 NTU; 5.2-25.4 mg/l, 4.05-27.23 mg/l; 2.2-13.2 mg, 0.49-6.41mg/l; 103 15-604.29 mg/l, 44 9-191.42 mg/l; 0.00- 0.23 mg/l, 0.0 4- 0.19 mg/l; 0.00-0.27 mg/l, 0.01-0.19 mg/l for dry and rainy season, respectively. E-coli and T-coli values of the samples ranged from 16-64 mg/l; 20-52 mg/l and 20-64 mg/l; 12-68 mg/l for dry and rainy seasons, respectively. The mean effect of the tested parameters in the ten (10) wards is significantly (p<0.05) different for rainy and dry season. The developed water quality map indicated the strength of contaminants present in water in Ogbomoso North LGA. Hence treatment will be required for the wells investigated before domestic use.