The purpose of this paper was to assess the influence of the city of Przemyśl on the quality of water in the San River. The water analysis carried out by the Voivodeship Environmental Protection Inspector in Rzeszów as part of the operational monitoring in 2014 and in 2017 was used in the study. The concentrations of selected physicochemical indicators determined in two measurement and control points located above and below the city of Przemyśl were taken into account. For each water quality indicator, the minimum and maximum values were determined and the arithmetic averages from the research period were calculated. In addition, the regularly performed indicators were subjected to a detailed statistical analysis. Box plot graphs show the extreme values, the median and the interquartile range. Water quality has been assigned to the appropriate class and category of surface waters. Selected specific pollutants and priority substances in the river water were also analysed. Only the concentration of benzo(a)pyrene at the measuring points did not comply with the environmental quality standards. It was found that the city of Przemyśl has a small influence on the quality of water in the San River. Although there was a deterioration of water quality at the measurement and control point below the city, its class and category did not change.