This research analysed water quality in three selected estuaries in New South Wales (NSW) which include Belongil Creek, Parramatta River, and Hunter River, using data from the NSW Estuary Water Quality Monitoring Program. Key parameters examined included temperature, chlorophyll-a, electrical conductivity, salinity, pH, dissolved oxygen, turbidity, ammonia-nitrogen, total nitrogen, and total phosphorus. The mean values of these parameters were compared against the Australian and New Zealand Guidelines for Fresh and Marine Water Quality (ANZG, 2018–current). Correlation analysis was also conducted to explore relationships between the parameters. Findings indicate that all three estuaries exhibited elevated nutrient levels, high turbidity, and variable pH, salinity, and dissolved oxygen levels often exceeding guideline thresholds. These conditions are likely due to surrounding urban and agricultural land use, contributing to nutrient pollution, industrial discharge, and agricultural runoff. This research is significant as it provides critical insights into the status of water quality in the selected estuaries, identifying potential environmental and anthropogenic impacts. The findings will support effective management strategies and policy decisions to protect estuarine ecosystems and maintain sustainable water resources.