In kidney and intestine, epithelial resorption of various amino acids, across the luminal brush border membrane, is mediated by different cotransporters. Neutral amino acids are thought to be transported by system B0, in particular an important player is the cotransporter (symporter) B0AT1 (SLC6A19) that belongs to a cluster of orphan transporters within the family of Na+- and Cl–dependent neurotransmitters and amino acid transporters (SLC6). B0AT1 is a Na+ – dependent, nutrient transporter that accepts a wide variety of neutral amino acids. The first fish ortholog of this transporter, sea bass B0AT1 (Dicentrarchus labrax) was cloned and electrophysiologically characterized by heterologous expression in Xenopus laevis oocytes. The substrate selectivity was estimated by recording the transport associated currents generated in the presence of different amino acids by the classical two-electrode voltage-clamp technique. The apparent affinity for Na+ and substrates was determined and our data were compared with those reported for the mouse and human orthologs displaying high similarities. The results showed that the most transported substrate was Leucine and despite the fact that B0AT1 could transport a broad range of neutral amino acids, this transporter, was also able to transport, with high efficiency, the charged Histidine. pH and ion-dependence was also analyzed; sbB0AT1 presented a weak pH-dependence and the substitution of Na+ with Li+ gave rise only to a small current like the mammalian orthologs. The characterization of this transporter in fish has a nutritional importance, in particular in cultured species, for its ability to transport EAA (essential amino acids).