This study assesses the hydrochemical dynamics of surface waters in Ukraine's border regions with Poland and Slovakia over a 15-year period. Key water quality parameters, including sulfates (SO₄²⁻), biochemical oxygen demand (BOD₅), dissolved oxygen (DO), and total suspended solids (TSS), were analysed to determine the ecological state of these transboundary water bodies. The results indicate that sulfate concentrations remain below the maximum permissible concentrations (MPC) for both household and fishery water use. BOD₅ and DO levels generally comply with environmental standards, though localized areas show signs of organic pollution. TSS concentrations remain within acceptable limits, likely influenced by natural erosion and occasional anthropogenic activities. Pearson correlation analysis revealed significant relationships between nitrogen and nitrates (r = 0.814), underscoring the role of agricultural runoff in nutrient dynamics. Negative correlations between DO and several pollutants suggest that organic and chemical contamination affects oxygen availability. These findings emphasize the need for continued monitoring and transboundary collaboration to safeguard water quality in the region.