This paper shows the results obtained in field analysis performed at the Tamiš River, starting from the settlement Jaša Tomić (the border between Serbia and Romania) to Pančevo (the confluence of Tamiš into the Danube). The Tamiš is a 359 km long river rising in the southern Carpathian Mountains. It flows through the Banat region and flows into the Danube near Pančevo. Over the years, the water quality of the river has severely deteriorated and badly affected the environment and the river ecosystem. In situ measurements enabled determination of physico-chemical parameters of water quality of the Tamiš River at every 400 m of the watercourse, such as: water temperature, pH value, electrical conductivity, contents of dissolved oxygen and oxygen saturation. The main reason of higher pollution of Tamiš is seen in connection to DTD hydro system. Sampling was performed at 7 points with regard to color, turbidity, total hardness, alkalinity, concentration of ammonium nitrogen, nitrite nitrogen, nitrate nitrogen, iron, chlorides and sulphates in samples. The aim of the present work was to evaluate water quality in the Tamiš River taking into account significant pollution, which originates from settlements, industry and agriculture, and to suggest appropriate preventive measures to further decrease the pollution of the river's water.