The phytoplankton community in three stations at Samarra Reservoir was studied seasonally. A total of 149 taxa were identified, ten of which were new additions to the Iraqi flora. The density ranged from 0.43 to 18.56 10³ ind. cm-³, Bacillariophyceae were found to be the dominant group. Variation in species dominance between seasons and stations was observed. The density of phytoplankton, chlorophyll ɑ concentration, and the share of Cyanophyta and Euglenophyta were higher at the station polluted with municipal sewage.