ABSTRACT The main purpose of this study was to assess the causes of illegal water connection and the impact on the performance of Ghana Water Company in production, billing and revenue generation in Ashanti North Region. The researcher used descriptive research design for the study. Quantitative and qualitative research approaches were used. The population was made up of the staff and customers of Ghana Water Company in the Ashanti Region. The total population for the study was Nine Thousand Seven Hundred and Eighty-Three (9783). Purposive and convenience sampling techniques were used to select three hundred and forty-six (346) respondents for the study. Questionnaires were the main instrument used for data collection. The main statistical techniques such as frequencies, percentages, tables and charts were used to explain certain findings. The study results concluded that the factors that motivate customers to connect water illegally to their premises were expensive new service connection fee, when pipe connection network is not available in their area, when they do not want to be billed on monthly basis, when the landlord is not willing to pay for the connection fee, and ignorance and inadequate knowledge on illegal connections can result in illegal water connections. The impact of illegal water connection on Ghana Water Company in Ashanti North Region were that illegal water connection increases water leakages and loss of water resources, illegal water connection can decrease company revenue and profitability, illegal water connection leads to decrease in water pumping capacity and decrease in productivity. The prevalence of illegal water connection in the study area was high. The study recommended that; the Ghana Water Company limited need adequate human, financial, technical and administrative resources to fulfill their mandate, including a professional and qualified workforce to monitor illegal connections.