Nilüfer stream in Bursa, Turkey, is important for being a huge resource for irrigation and also the wastewater discharge point of many treatment plants. There are lots of factories dealing with textile and food industries and also municipal waste treatment facilities that directly discharge their wastewaters into the stream and may lead to pollution. In this research, we aimed to determine the seasonal variation of some trace element and heavy metal concentrations of Nilüfer stream and the treatment plants. Water samples were taken from the treatment plants and from the stream that the treatment plants discharged to at four different periods during August 2013 to May 2014. Discharges from the treatment plants affected the quality of the stream negatively (p<0.01) and varied depending on the sampling periods and also depending on the processed products at the factories and also their discharges from the treatment plants. Although the Zn, Al, Ni, Pb, and Co concentrations of the water samples were found to be under the limits of the World Health Organization (WHO), the Food and Agriculture Organization of the United Nations (FAO) and Treated Water (TW), concentrations of especially Fe, Cu, Mn, Cd and Cr were found to be over the limitations of TW.