Understanding the diversity patterns of macroalgae assemblages in the coastal Mediterranean of Alexandria is important for seawater management. To elucidate the diversity patterns in macroalgae communities, five Mediterranean sites (Eastern Harbor (EH), Abu Talat (AT), El Mex Bay (EM), SidiBishir (SB) and El-Tabia pumping (TPS) were examined during June 2019. Macroalgae found on the Alexandria coast was 5 species namely, Ulva Fasciata, Ulva Compressa, Corallina Officinalis, Carollina Elongate and PetrocladiaCapillacea. Patterns of alpha and beta diversity were evaluated across macroalgal habitats, in relation to different levels of heavy metal accumulation and physicochemical parameters. We found significant spatial differences in alpha diversity and moderate value of the beta index (average ~ 0.6) explained by the high variation of pollution by heavy metals. The abundance of the Ulva fasciata is higher than those of other macroalgae. EH is the location that has the highest diversity index value (H’), the richness index of species (D), the highest evenness index (E), and Simpson index 1.28, 0.33, 0.59, and 0.69 respectively.