Sponges harbor complex and diverse microbiomes that contribute to the host’s fitness and, ultimately, the health of the ecosystems sponges inhabit. Here, using high-throughput 16S and 18S rRNA amplicon sequencing, we explore the prokaryotic and eukaryotic communities associated with three sympatric Mediterranean demosponges, namely Tethya aurantium, Tethya meloni, and Tethya citrina. We found species-specific prokaryotic and eukaryotic communities despite the close sympatry of the three Mediterranean Tethya species studied. This offers further support for the phyletic nature of the sponge microbiome and indicates that the sponge-associated eukaryotic communities also display similar levels of specificity.