Ela-ela beach has wide seagrass ecosystem with sandy substrate. Sea grass is a habitat of various invertebrates including mollusks. Some mollusks live by burrowing in substrate and attaching to seagrass leaves. A study of mollusks diversity of Ela-ela Beach, Sekotong Lombok Barat regency NTB was conducted on July 2012. The objective of this study was to estimate the abundance and diversity of mollusks. Parallel quadrate transect was applied as the sampling methods. Ninety two individuals were collected and identified, consisting of Gastropods (29 species), Bivalves (6 species). The most abundant species in this studied area were Trachycardium rugosum (18 individuals) and Pyrene scripta (17 individuals). The Diversity Index (H’) was 2.99, the Pielou Index (J) was 0.84, and the Margalef Index (d) was 17.31. Based on Odum (1994), the Diversity Index is moderate.