Biological fouling has caused a lot of concern in marine industries due to the attachment of microorganisms including bacteria, algae, and diatoms on a marine surface to create a biofilm. Biofouling causes negative impacts on the marine industry such as an increase in weights of hulls, low speed, and high fuel consumption. In the recent past, nanoparticles have attracted a lot of attention in the fields of material science, chemistry, and biology owing to their rare biological properties. Silver nanoparticles (AgNPs) have been long known for its strong toxicity against a wide range of microorganisms. Herein, we synthesized the AgNPs via a green synthesis approach known for its benefits such as one-pot, inexpensive, and eco-friendly; by using Illicium verum (IV) extract as a demoting and sustaining agent. Further, characterization tests of obtained AgNPs-IV were investigated including Ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and Atomic force microscopy (AFM). The UV-Vis result confirmed the AgNPs-IV formation with its surface Plasmon resonance peak. FTIR was tested to investigate the bio-functional groups liable for the AgNPs-IV synthesis. XRD peaks also meet with the standard of AgNPs (JCPDS: 41-1402). SEM, TEM, and AFM analysis of AgNPs-IV showed the hexagonal structure with 14.56 nm mean size. The cell growth of diatom on 5 th day with blank sample suspension was 2.308 (Cell 10 5 number/mL), while for AgNPs-IV sample suspension was 0.19 (Cell 10 5 number/mL). The green synthesized AgNPs-IV showed excellent antidiatom activity against Paeodactylum Tricornutum (P. Tricornutum) marine diatom.