In this study, some heavy metal concentrations (Cu, Cd, Pb, Cr, Mn and Zn) were seasonally determined in water to evaluate of the quality of the Beyler Dam Lake. The average concentrations of heavy metals analyzed in water samples for cold and hot season were Cu: 11.53, 13.23; Cd: 0.85, 0.97; Pb: 13.77, 16.26; Cr: 2.88, 3.48; Mn: 1.94, 1.71; and Zn: 7.57, 8.20 ppb, respectively. The annual average (AA) concentrations of heavy metals were Cu: 12.38; Cd: 0.91, Pb: 15.01, Cr: 3.18; Mn: 1.82; and Zn: 7.88 ppb. In general, the heavy metal concentrations were found to be higher in hot season than the cold season. It was observed that none of the heavy metals assessed exceeded the limits specified in the Turkish Water Pollution Control Regulation. The Beyler Dam Lake was classified as Class I for all the heavy metals except Pb for which it was classified as Class II. These results indicate that the lake is not polluted by the heavy metals. However, relatively high Pb levels seek further research to identify the source. The lake water can be used for agricultural activities but should continue to be monitored.