This study investigates the capability of marine Aspergillus flavus amylase (Amy) to synthesize silver nanoparticles (AgNPs) and studies its impact on Dicentrarchus labrax(sea bass)larvae growth performance. Characterization of Amy-AgNPs was carried out by FTIR, UV–Vis's spectroscopy, and SEM. The effect of Amy-AgNPs on antimicrobial and antioxidant activities was studied. The colloidal brown color of Amy-AgNPs with FTIR analysis indicated that amylases had the responsibility for capping the produced nanoparticles and making them more stable. Spherical Amy-AgNPs had sizes of 22.88 to 26.35 nm. Significantly, Amy-AgNPs inhibited the growth of fish-tested microbes by a maximum zone of inhibition, 13-20 mm and maximum MICs ranged from 1.6 to 6.3 µg/ml. Also, it acted as scavenged DPPH by 31.46 to 94.0 %. Sea bass larval morphometric measurements including mean total length (TL), width (W), total weight (TW), larvae survival percentage (%) and specific growth rate (SGR) were recorded, compared to the control group using different concentrations (1, 5, 10, 20%) of encapsulated Amy-AgNPs during larval feeding regime for a period of four weeks. The results revealed that 5% Amy-AgNPs was significantly the most effective concentration at P < 0.05 and achieved higher survival percentages; 51±2.8% and increased the specific growth rate by 16.23±0.62%.