A green synthesis of silver nanoparticles (AgNPs) was conducted by using Psidium guajava (P. guajava) leaf extract under light-emitting diodes (LED) irradiation. The obtained AgNPs were characterized by ultraviolet–visible spectroscopy, X-ray diffraction , energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy, and transmission electron microscopy (TEM). In comparison to the absence of LED irradiation, the rate of AgNPs formation has been increased by more than twice with LED irradiation. Among LED irradiations, blue LED offered the most efficient in the formation of AgNPs. TEM analysis revealed that both AgNPs-N (without LED irradiation) and AgNPs-L (with LED irradiation) were nearly spherical with an average size of 32 nm.The antimicrobial assay indicated that AgNPs-L exhibited better antimicrobateria than AgNPs-N. The best antibacterial activity of AgNPs-L was recognized on L. fermentum (IC₅₀ = 4.0 pM) for gram-negative bacteria, P. aeruginosa (IC₅₀ = 3.5 pM) for gram-positive bacteria, and C. albicans (IC₅₀ = 4.6 pM) for fungi.