Abstract Human-driven environmental changes in the ocean are reshaping the diversity and distribution of coastal organisms. Understanding species diversity is essential for assessing threats, predicting impacts, and guiding conservation planning. Our study focuses on the family Leptocheliidae (Crustacea: Tanaidacea), a suitable model for investigating diversity and distribution in low-mobility crustaceans. This family, abundant in shallow waters and sensitive to environmental shifts, was analyzed at global scale using literature, databases, and unpublished data from Australian coral reefs. Species richness, estimated richness, and sampling effort were calculated organizing data into latitudinal bands and ca. 800,000 km hexagonal cells. Cluster analysis by biogeographic provinces was used to identify distinct species assemblages Generalized Linear and Additive Models (GLM, GAM) assessed environmental drivers, including temperature, productivity, chlorophyll, dissolved oxygen, salinity, silicate, phytoplankton, nitrate, and phosphate. Results revealed a bimodal species richness pattern, with diversity peaking in lower latitudes and declining at the equator. Biodiversity hotspots were identified in the Indo-Australian region, central Indo-Pacific, Gulf of Mexico, and Caribbean, with high estimated richness in the Mediterranean and SE Australia. The subpolar region displayed distinct, but low-diversity assemblages. Among the environmental variables, dissolved oxygen was identified as the most important factor influencing species diversity and estimated diversity across latitudes, followed by temperature. Models incorporating salinity were the most reliable for species diversity within hexagonal regions.