Lake Edku is the third largest in the system of the northern coastal wetlands in Egypt. Itis situated on the west part of NileDelta and is considered as an important fishing area in Egypt. The Lake is a shallow basin of brackish water, nutrient replete system (particularly phosphorus and nitrogen), suffers from high levels of aquatic vegetation and from the expansion in fish farming and agricultural discharges. Ecological and biological status of Lake Edku was evaluated depending on seven years of seasonal monitoring from summer 2009 to winter 2016, at 9 stations representing the different regions within the Lake. Water transparency averaged 25.47 ± 7.56 cm. The water temperature was23.54 ±5. 84 °C and water salinity was 2.24 ± 2.12 PSU. The dissolved oxygen was 9.37 ± 1.85 mg O2/L, the biological oxygen demand was 17.56 ±15.19 mg O2/L and the Chlorophyll-awas 90.23± 52.85 mg Chl-a/m3.The recognized phytoplankton species were 309 taxa from 93genera and six classes were recorded: 118 Bacillariophyceae, which formed 47.31% by number of the total phytoplankton standing crop, 93Chlorophyceae (44.6%),58 Cyanophyceae (5.51%), 27Euglenophyceae (2.02%), 12 Dinophyceae (0.56%) and one species for Silicoflagellate. The present study revealed that the phytoplankton abundance and community are controlled by the environmental conditions, which fluctuatefrom one year to another, so while the phytoplankton seasonal succession. Generally speaking, a decrease was noted in the phytoplankton densities between 2009 and 2016. Phytoplankton diversity, varied broadly from 0.25 to 3.38, low values were accompanied by stable commu-nity, while higher diversities corresponded to non-steady state periods. Similarity was estimated for each and eve-ry single separate year and discussed.