River pollution remains a serious environmental issue in Samarinda, Indonesia, largely driven by domestic waste and human activities along riverbanks. This study aims to assess the relationship between community knowledge, attitudes, and practices toward environmental health and to evaluate the physical and chemical quality of river water. A cross-sectional survey was conducted among 130 respondents using a structured questionnaire, and water samples from ten locations were analyzed for turbidity, Biochemical Oxygen Demand (BOD), Chemical Oxygen Demand (COD), conductivity, pH, and salinity. Results showed that 62.3% of respondents had high knowledge, but only 7.7% demonstrated good environmental practices. Statistical analysis revealed weak yet significant correlations between knowledge and practice (r = 0.217; p = 0.013) and between attitude and practice (r = 0.206; p = 0.019). Water analysis indicated high turbidity (up to 39.10 NTU), COD levels above 10 mg/L, and acidic pH values (5.0–5.8), exceeding the national standards. These findings highlight the gap between environmental awareness and behavior, alongside poor river water quality. Strengthening community participation, environmental education, and enforcement of water quality regulations are essential to promote behavioral change and improve river ecosystem sustainability.