Most major urban centers in Sub-Saharan Africa are located along the shores of estuaries, lakes, or lagoons which, due to their high biodiversity, are often subjected to significant anthropogenic pressures, particularly waste pollution. This study aims to analyze the phytoplankton community structure of the Ebrié Lagoon, an ecosystem heavily impacted by human activities. Phytoplankton samples were collected between February and November 2020 using a 20-µm mesh plankton net, targeting specific areas of the lagoon exposed to intense anthropogenic pressure. A total of 53 taxa belonging to five phyla were identified: Heterokontophyta, Dinophyta, Cyanoprokaryota, Euglenophyta, and Chlorophyta. Among these groups, Heterokontophyta exhibited the highest diversity, accounting for 58% of the total abundance. Furthermore, Cocody Bay emerged as the most biodiverse site, with 45 species recorded, representing 46% of all identified taxa. These findings highlight the ecological importance of the Ébrié Lagoon as a phytoplankton habitat and emphasize the urgent need for management strategies to safeguard this fragile ecosystem against increasing urbanization.