In our previous studies we assessed the biochemical response of juvenile seabream to the exposure to three selected polycyclic aromatic hydrocarbons (PAHs) (phenanthrene, pyrene and fluorene) in short-term laboratory experiments. Since in the analyses conducted in the field it is much more natural to expect the presence of multiple contaminants at the same time, the objective of this study was to analyse the reaction of seabream to the exposure to a mix of the three PAHs tested previously. The proportions of the individual components in the PAH mix used in our experiments were constant and determined on the basis of the concentration addition concept. We measured a set of hepatic biomarkers: 7-ethoxyresorufin-O-deethylase (EROD), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) and lipid peroxidation; as well as biliary fluorescent aromatic compounds (FACs) metabolites. Moreover, we calculated the biotransformation index, the condition factor and the hepatosomatic index. Only a few of these indicators provided statistically significant response to the tested exposures, while FACs showed very strong increase with increasing concentration of the tested mix of PAHs. The results of this research are expected to contribute to the establishment of a good biochemical index of exposure to mixtures of PAHs in laboratory experiments, which can be further useful in field studies dealing with the impact of organic pollutants on marine organisms.