Biological Oxygen Demand (BOD) is generally used for determining water pollution levels in bodies of water. Estuary is a semi-enclosed body of water that can be polluted via land areas or rivers. This study was conducted to determine the spatial distribution of water pollution levels in the Suwung Estuary in Bali based on BOD₅ analyses conducted in January and February 2016. Samples were taken in 20 points (19 points in the Suwung Estuary and 1 outside the Suwung Estuary as control). BOD₅ samples were then analysed in the laboratory. Our BOD₅ analyses used the amperometric method based on the National Field Manual for the Collection of Data Water-Quality, Chapter A7. BOD₅ samples were taken at all tide cycles, during low to high tide and high to low tide. BOD₅ values ranged from 0.84 mg/L–9.47 mg/L during lowto high tide and 0.96 mg/L–8.75 mg/L during high to low tide. Results of the BOD₅ analyses showed slight contamination in the Suwung Estuary during both tidal conditions. The BOD₅ values’ spatial distribution showed higher values around cage aquacultures, rivers, the Suwung Landfill, and around the Benoa Harbour.