This study was conducted to determine the concentration of boron in the waters of the Gediz River. According to the results, the boron concentrations ranged from 0.125 to 4.548 mg/L. The average boron value (2.428 mg/L) was compared with “Environmental Regulations, Water Pollution Control Regulations and Quality Criteria for Inland Water Resources by Class”. The Gediz River was determined as class IV (very polluted) in terms of the boron parameters. It was concluded that the reason for the high boron values were natural and/or industrial discharges at some stations.