Aquaculture industry in the Mediterranean region exhibits a growing interest for the Mediterranean meager Argyrosomus regius. Some preliminary works showed a good growth performance of the species in nearly isosmotic salinities. However, the patterns of alteration of prolactin (Prl) as well as growth hormone (Gh)/insulin growth factor-1 (Igf1) axis at the molecular level are not yet described in this species. Therefore, we cloned and sequenced partial cDNAs for pituitary prolactin (prl) and growth hormone (gh), hepatic insulin-like growth factor (igf1), and β-actin (actb). Expression patterns of these transcripts were tested in juveniles of A. regius acclimated to four different environmental salinities: (1) 5 ‰ (hyposmotic); (2) 12 ‰ (isosmotic); (3) 38 ‰ (hyperosmotic; seawater control); and (4) 55 ‰ (extremely hyperosmotic). All investigated transcripts shared high sequence identities with their counterparts in other perciformes. prl mRNA levels showed inverse pattern with increasing salinities. gh mRNA enhanced significantly in both 12 and 55 ‰ salinity groups in comparison with the control group, while igf1 showed its maximum expression levels under the nearly isosmotic environment. The results indicated clear sensitivity of prl, gh and igf1 to changes in environmental salinity, which can possibly control the euryhalinity capacity of this species.