This study was carried out between April, 2002 and April, 2003 at four stations in Mamasin Dam Lake in the Central Part of Anatolian Region of Turkey. Sixty phytoplanktonic algal taxa were recorded at these stations. These were consisting of species belonging to divisions of Ochrophyta (=Bacillariophta), Chlorophyta, Charophyta, Cyanobacteria and Euglenozoa. Generally, members of Ochrophyta group were dominant in the lake. Some physical and chemical water quality parameters were determined and these were related with chlorophyll-a values.