This study aimed to study the settlement of fouling organisms in the Eastern Harbor of Alexandria during the period from 2019 to 2020. Seasonal samples of marine fouling invertebrate species had been collected using white roughened wood test panels. Some environmental parameters (temperature, transparency, salinity, pH, and dissolved oxygen) were studied. The fouling invertebrate species and taxa were identified and classified. Statistical analysis was conducted using primer and paste software. The results of this study showed that some environmental parameters such as dissolved oxygen and water temperature of marine water in Eastern Harbor, Alexandria can significantly affect the settlement of fouling organisms. The results showed also that the fouling was composed of 37 invertebrate species, belonging to 23 families, within 12 orders, 7 classes, and 6 phyla. The highest diversity phyla were Crustacea (20 species from 11 families), followed by Bryozoa (7 species from 7 families) and Annelida (6 species from 2 families). The biomass of fouling invertebrate families and their species varied in different depths. The most heavy families were Serpulidae and Balanidae. At 0.5 m depth, Hydroides elegans had the mostly heavy biomass (2720.2±1716.3 g/m²); followed by Balanus amphitrite (889.3±687.4 g/m²). At 1.5 m depth, also Hydroides elegans had the heavy biomass (2264.6±2506.7 g/m²); followed byBalanus perforates (1691.3±3198.3 g/m²). Seasonal variation in fouling invertebrate biomass showed that Hydroides eleganes represented the heaviest recorded biomass during spring, summer and autumn, while Balanus amphitrite was the heaviest biomass observed during winter.