Seasonal variations in macroalgae community inhabiting Port Said coast were investigated during the period from summer 2004 to spring 2005. Species composition and percent cover of macroalgae were studied in four sites distributed along the coast, representing different habitats. Some hydrographic parameters (temperature, salinity, pH, dissolved oxygen, phosphate, nitrite, nitrate and silicate) were measured to determine the water characteristics influencing the studied sites. The study revealed the presence of 55 species, of them, 17 species have not been recorded previously in this area. The macroalgae comprised 31 species of Rhodophyta, 21 species of Chlorophyta and 3 species of Phaeophyta. Of the recorded species, 16 species occurred as epiphytes; most of them belonging to Rhodophyta. The most abundant species were Cladophpora prolifera, Enteromorpha compressa, E. prolifera, E. flexuosa, E. intestinalis, E. ralfsii, Ulva fasciata and U. rigida from Chlorophyta, and Gelidium crinale and Hypnea cornuta from Rhodophyta. There were relatively seasonal and spatial differences in the distribution patterns of species composition and abundance. Autumn and summer were the most diversified seasons. Site I which was away from any effluent, rich and diversified flora were observed relative to the other sites, with the highest abundance especially in Rhodophyta. The influence of the brackish water of Lake Manzala was obvious on the vegetation at site IV and sometimes at site III.