The quality of groundwater in Port Harcourt was investigated in order to understand the status at different points within the city. This was achieved by obtaining water samples from thirty (30) boreholes evenly distributed within the city at a frequency of three months for a period of one year. The water samples were analyzed for turbidity, total dissolved solids (TDS), pH, electrical conductivity (EC) chloride (Cl), sulphate (SO4), nitrate (NO3) and phosphate (PO4). Others include biochemical oxygen demand (BOD), chemical oxygen demand (COD), total coliform (TC), iron (Fe), lead (Pb) and manganese (Mn). The laboratory results associated with the various sampled boreholes were subjected to Canadian Water Quality Index (CWQI) and it was noted that the groundwater quality of the sampled boreholes ranged between 76.73 – 35.60 on the Canadian index. The index values at the non-sampled boreholes were obtained by mapping the groundwater quality of the entire city using Inverse Distance Weighted (IDW) interpolation technique. The generated map revealed that the quality of groundwater in Port Harcourt deteriorate towards the southern part of the city. Notwithstanding, it was concluded that the groundwater quality within the entire city were either occasionally, frequently or always threatened by anthropogenic and (or) geogenic factors based on the range of the Canadian index values determined.