Balingasay River in the Philippines is a protected seascape with rich mangrove areas that support diverse life forms. Gastropod diversity in an ecosystem also represents the status of environment, richness of biodiversity, and the diversity of life forms in the river. This study aims to determine the composition of gastropods and its diversity in the Balingasay River. Gastropod composition, abundance and diversity were observed by analyzing snail samples observed and collected from two sites along the riparian zone of Balingasay River. A total of seven marine species of gastropods were identified from the 253 collected individuals. It was noted that species under family Neritidae and Potamididae are abundant within the sampled areas. Neritina turrita was found to be most abundant with 59.69% of the total gastropods collected and followed by Littoraria scabra with 11.86% composition. In addition, seaward portion of the river has the higher snail diversity and high species richness compared to the inward area. While the inward area has high dominance compared to the seaward area of the river. In summary, marine species are found to be present in the estuarine to freshwater environment which indicates the ecological diversity of the mangrove and estuarine ecosystem of the river.