This study investigates the abundance, diversity, and community composition of mollusks in two distinct habitats—breakwaters and mud-sandy flats—along the Iraqi coast in Al-Faw City, Persian-Arabian Gulf. Quantitative sampling recorded 7,811 individuals across 24 species from 19 families, including several species newly documented in Iraq. Species richness and diversity indices revealed higher mollusk diversity in breakwaters, which supported 17 species compared to 10 species in mud-sandy flats. Breakwaters provided structurally complex habitats, fostering higher species richness and more balanced distributions, as evidenced by Shannon-Wiener Diversity (H' = 2.63) and Pielou’s Evenness Index (J' = 0.83). In contrast, mud-sandy flats, characterized by uniform substrates, exhibited lower diversity (H' = 1.86; J' = 0.59) and fewer ecological niches. Bray-Curtis dissimilarity (0.76) highlighted significant compositional differences between habitats, driven by key species such as Cerithium scabridum and Assiminea mesopotamica. These findings underscore the importance of artificial structures like breakwaters in enhancing coastal biodiversity and provide critical insights for habitat conservation and management in the Gulf region.