Six (6) samples were obtained from boreholes and monitoring wells in the vicinity of the Oke-Diya landfill sites in Sagamu, Ogun State. The pH, EC, TDS, Total Hardness, Chloride content, Total Alkalinity, and Nitrate content were examined in both the water samples gathered. The findings were examined and contrasted with the World Health Organization (WHO-2011) and the Nigerian Standard for drinking water quality (NSDWQ-2007). Certain levels of physio-chemical parameters at Oke-Diya dumpsite were discovered to be elevated, especially in EC and TDS, whereas Chloride levels indicated that OD-3 and OD-4 exceeded the established standards (WHO&NSDWQ). The elevated chloride levels found in groundwater samples OD-3 and OD-4 indicate that the contamination is likely originating from sewage sources. The study areas revealed that the pH levels in the ground water samples are slightly acidic in nature. This could be due to dense population and commercial activities in those regions. Total Alkalinity, Dissolved Nitrate, and Total Hardness levels in the water samples comply with NSDWQ and WHO standards except for Total Hardness in OD-4 which is above the permissible limit. The study suggests that poorly designed landfills and hazard waste disposal into water bodies may result in significant groundwater contamination, posing risks to human health and the environment. Hence, it is necessary for both community members and the government to work together to prevent careless waste disposal and to implement effective waste management and monitoring in locations where landfills exist