A European sea bass (Dicentrarchus labrax) weaning trial was conducted from the 35^th to the 50^th dph. Larvae were reared and fed on enriched rotifers and Artemia in the same 2 m² tank from 3 to 34 dphin NIOF hatchery larval rearing unit. In the present study, the total antioxidant capacity (TAC), superoxide dismutase activity (SOD), catalase (CAT) activity, and some hepatic enzymes in early life stages after exposure to four treatments in triplicates: green water control (G), marine synbiotic (MS), estradiol (E2), MS and E2 mixture (ES) treated micro-diets were investigated. The larval length, growth weight, and survival considerably decreased in the E2 vs. the other treatments, mixing MS with E2 in ES treatment increased significantly larvae growth and survival compared to E2 and G control. The total protein significantly decreased in larvae exposed to the E2 treatment compared to the other treatments. Furthermore, albumin was significantly reduced after E2 treatment, while globulin significantly increased after MS treatment. Larvae fed ES showed the highest body glucose in g/l. The aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities decreased significantly after E2 treatment compared to all other treatments, while ES treatment increased them significantly compared to E2 treatment. The alkaline phosphatase (ALP) activity increased significantly after MS treatment compared to all other treatments. Triglycerides (TAG) increased significantly after E2 treatment vs. the other treatments. The SOD and CAT activities increased considerably, while TAC showed a significant decrease after E2 treatment vs. all other treatments. SOD and CAT activities were significantly reduced, while TAC showed a significant increase after ES treatments compared to E2 and G treatments. In conclusion, mixing MS with E2 in ES treatment decreased the negative impacts of E2 in the European sea bass larval growth, survival and antioxidant capacity.