Mollusk has a role as a food source in benthic ecosystems. Presumably, there has been a decrease in its diversity on the protected coastline of Berbak-Sembilang National Park (BSNP) due to fluctuations in water quality parameters that threaten the sustainability of another biota in the web food system. The purpose of this study was to describe the diversity of mollusks and their correlation with water quality in the protected coastline area. The research methodology was carried out, namely: water quality data collection, mollusk sampling, diversity analysis, and correlation analysis. Principal component analysis and similarity analysis were used. The results showed that there were 28 species of mollusks, which were classified into two classes: Bivalvia (79%), and Gatropoda (49%), with 21 species. The mollusk abundance means 263.25 ind.m-2, and the diversity is categorized as low H'1 except stations 2 and 4. It is supported by the dominant species, namely Anadara granosa (36.61%), and Nutricola sp. (35.47%. There are two clusters of mollusks: open coastal areas are characterized by higher temperatures, nutrients, salinity, pH, currents, and brightness, and estuary clusters are characterized by higher dissolved oxygen and mollusk abundance.