This study was directed at Wasit Thermal Power Plant (WTPP) to determine the water quality status. Nine sampling stations established along the reach of Tigris River, the first station was 500m upstream (US) to WTPP and it was a reference station, the second station at WTPP and seven stations downstream (DS) to WTPP for collection of water samples. Water samples were prepared for their physico-chemical characteristics at all sampling stations were compared with the reference station. Sampling of all stations (downstream to WTPP) showed higher water pH, total dissolved solids (TDS), electrical conductivity, and chemical oxygen demand (COD) than that of sampling station upstream to WTPP and lower water dissolved oxygen (DO). The results showed increasing of pH, TDS, EC, and COD by 68%, 166%, 60% and 478% respectively, and decreasing the value of DO by 66% indicated that discharge from WTPP increased pollution load in river Tigris.