Salinity is one of the most crucial environmental factors that structures biogeographic boundaries of aquatic organisms, affecting distribution, abundance, and behavior. However, the association between behavior and gene regulation underlying acclimation to changes in salinity remains poorly understood. In this study, we investigated the effects of salinity stress on behavior (movement distance) and patterns of gene expression (using RNA-seq) of the intertidal gastropod Batillaria attramentaria. We examined responses to short- (1 hour) and long-term (30 day) acclimation to a range of salinities (43, 33 (control), 23, 13, and 3 Practical Salinity Units (PSU)). We found that the intertidal B. attramentaria is able to tolerate a broad range of salinity from 13 to 43 PSU, but not the acute low salinity of 3 PSU. Behavioral experiments showed that salt stress significantly influenced snails’ movement, with lower salinity resulting in shorter movement distance. Transcriptomic analyses revealed critical metabolic pathways and genes potentially involved in acclimation to salinity stress, including ionic and osmotic regulation, signal and hormonal transduction pathways, water exchange, cell protection, and gene regulation or epigenetic modification. In general, our study presents a robust, integrative laboratory-based approach to investigate the effects of salt stress on a non-model gastropod, which is facing detrimental consequences of environmental change. The current genetic results provide a wealth of reference data for further research on mechanisms of ionic and osmotic regulation and adaptive evolution of this coastal gastropod.