Tenacibaculum soleae is a recently described pathogen that has been reported as the causative agent of considerable losses in sole cultures in Spain. This report documents the first case of T. soleae as an etiological agent of tenacibaculosis in farmed sea bass Dicentrarchus labrax. Its identification was performed employing phenotypical, serological and molecular methods. Although the sea bass isolates were homogeneous from a biochemical, chemotaxonomic and molecular point of view, they belonged to a serological group different from the type strain CECT7292, which can be of great importance in the development of future vaccines and other methods of disease prevention in sea bass industry. Virulence assays with a representative isolate confirmed the pathogenic potential for sea bass. The disease was experimentally reproduced by prolonged bath, while no mortalities could be recorded by intraperitoneal injection. The results presented here show that T. soleae must be taken into account as an important pathogen in the marine aquaculture industry.