The goal of this study was to develop a method that uses UV-Vis spectroscopy for the determination of residual polymer concentration water and environmental samples. UV-Vis absorbance measurements are quick and simple and can be usefully applied in research and practice. Five different polymers exhibiting a wide range of polymer characteristics were tested in the UV range of 200–300 nm. The incremental increases in polymer concentrations corresponded to incremental increases in absorbance measurements, and a strong linear relationship was established between the polymer concentration and the absorbance values. The method was successfully used in the determination of polymer concentrations in water samples, as well as in centrate samples collected from a wastewater treatment plant.