A simple new green method for the synthesis of silver nanoparticles (AgNPs) using the anti-oxidant compound curvularin isolated from the endophytic fungus Epicoccum nigrum ASU1 is reported for the first time in this article. The present work describes a one-step functionalization of AgNPs using compound curvularin as a reducing and stabilizer agent. The AgNPs capped curvularin were characterized by UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), selected area electron diffraction (SAED), energy dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HR-TEM). The results showed the formation of high purified spherical AgNPs with an average size of 37 nm. The FT-IR results suggested that both hydroxyl and carbonyl functional groups in curvularin are responsible for the reduction of the Ag+ ions and stabilizing AgNPs. The AgNPs showed potent antifungal activity at various extends compared to curvularin alone against the phytopathogenic fungus Alternaria solani.These findings emphasise that such biocompatible green nanoparticles, thanks to their potent antifungal activities, may be applied as new bio-fungicides against various plant pathogenic fungi in the field of plant protection and plant disease management.