Vibrios are bacteria responsible for a significant proportion of infections affecting marine invertebrates and represent the major cause of mortality in farmed marine species. They are able to colonize many habitats, existing as planktonic forms, in biofilms or associated with various hosts. This high adaptability is linked to their capacity to generate genetic diversity, in part through lateral gene transfer, but also by varying gene expression control. Thus, in vibrios, the evolution of virulence is intimately linked to genomic plasticity, transcriptomic versatility and the resulting ecological fitness. In contrast to species that are pathogenic to humans, little data are available regarding invertebrate pathogens. A few results have been gathered for some species, especially as far as colonization and invasion processes are concerned; however, recent advances in genomics and transcriptomic profiling alongside the establishment of domesticated animal strains will help to make up for our lack of knowledge of “non model” systems leading to new and original scientific questionings.