The bio-reduction of aqueous copper ions by the leaf/fruit extract of the P. guajava plant was demonstrated under both alkaline and acidic conditions. The resulting copper nanoparticles, characterized using UV-Vis, ATR-FTIR, SEM, and EDX, had an average particle size of 20-30 nm, as indicated by SEM analysis. The UV-Vis spectrum of CuNPs exhibited a characteristic peak at 352 nm, while EDX confirmed the presence of pure copper (54.15%) at energy regions of 1, 8, and 9 keV. ATR-FTIR revealed four distinctive peaks at 3235.3 cm -1 , 2109.7 cm -1 , 1640.0 cm -1 , and 1069.7 cm -1 for P.g-CuNPs, with the peak at 2109. Based on the study's findings, P.g-CuNPs derived from Psidium guajava can be utilized for various biomedical applications, serving as a therapeutic drug for enhanced efficacy against microbial infectious diseases. Furthermore, they can be incorporated into textile coatings for added antimicrobial properties and utilized in food storage by nanocapsulation to extend the shelf life of food items.