Intertidal rock platform ecosystems can be found all along the Western Australian coastline, supporting high invertebrate diversities and providing vital ecosystem services. This study aimed to describe the spatial distribution and diversity patterns of invertebrates on intertidal rock platforms. Our study surveyed 15° of latitude and 39 limestone platforms, utilising quadrat and timed search methods to record species richness and abundance. Multivariate analyses were used to examine components of diversity and a significant latitudinal gradient in alpha and gamma diversity was observed with species richness decreasing with increasing latitude at both site and latitudinal levels. Average taxonomic distinctiveness (Δ+) reported a similar pattern, with the taxonomic breadth of assemblages decreasing at higher latitudes. Beta diversity did not demonstrate a latitudinal gradient and was similarly high within and between latitudes. Cluster analysis was employed to identify five distinct invertebrate assemblage bioregions along the coast. Understanding the biogeography of coastal invertebrates acts as a valuable baseline in the face of climate change and can be used to inform future management actions. Previous global studies of intertidal communities have not included data for Western Australia, and this dataset helps to fill the vast knowledge gap for the Australasian region.