The feasibility of reducing the fish meal (FM) content, as much as possible, in juvenile seabass diets by using a combination of four plant nutrients (plant mix, PX): soybean meal, SBM; soyprotein concentrate, SPC; corn gluten, CG and maize flour, MF was investigated . Seabass (mean initial body weight, 4.74±0.04 g) were fed with one of four isonitrogenous and isolipidic diets formulated to progressively reduce FM concentration of control diet (CTRL), by incorporation the PX, to be 30% (FM30 diet), 25% (FM25 diet), and 20% (FM20 diet) over a 13-week growth period. Fish were fed the experimental diets in triplicate and the resulting effects on growth performance, nutrient utilization, biochemical and amino acid composition, major blood constituents, immunity indicators and intestinal histology were evaluated. At the end of the trial, the FM25-fed fish presented growth, feed utilization, and survival rates comparable (P>0.05) to the CTRL fish. In addition, this diet did not negatively influenced major blood constituents, immunity indicators or intestinal histomorphology. Further dietary FM reduction to 20% (FM20 diet) and elevation of PX inclusion level (~ 59%) have caused a significant (P<0.05)decline  in final fish weight, haemoglobin, erythrocyte, leukocyte and lymphocyte counts, elevated leukocytes phagocytic-activityand caused some abnormalities in the proximal intestine (PI) morphological features, but did not negatively impacted haematocrit value, mean erythrocyte cell volume (MCV), mean cellular haemoglobin content (MCH), mean cell haemoglobin concentration (MCHC), monocytes, eosinophils, serum total protein and lysozyme activity. Based on these results, the FM25 formulation (containing approximately 54% PX) can be considered the appropriate for reducing dietary FM down to 25% without compromising the performance, health, immunity or PI morphology of juveniles' seabass.