The distribution patterns of diatoms in the surface sediments of Manzala Lake have been studied in detail. A total of 110 diatom species belonging to 48 genera have been identified from samples consist mainly of greenish gray mud with relatively some muddy sand sediments. The distribution pattern of the recorded diatom taxa displayed changes in the floristic composition due to changes in the ecological conditions such as salinity, pH, and some chemical elements, which are related to sea-level fluctuations, freshwater influences, waste discharge from the drains and climatic changes. Multivariate statistical techniques including hierarchical ascending clustering and Canonical correspondence analyses were used to identify ecological groups of diatoms and to estimate which environmental variables were important in diatom distribution. Five diatom ecological groups were identified and classified the lake into five distinct ecological zones.