The increase in bacterial resistance to one or several antibiotics has become a global health problem. Nanocomposite have become a tool against multidrug-resistant bacteria. A nanocomposite, Ag₂O/SrO/CaO was prepared from AgNO₃, SrCl₂.6H₂O, CaCl₂, and a solution of Na₂CO₃ via calcination of the salts mixture. The nanocomposite was successfully prepared by the co-precipitation method and completely according to green chemistry, both in terms of synthesis method, solvent and precursors. The nanocomposite was characterized by XRD, XRF, FESEM analyses. Afterwards, the nanocomposite was applied for antibacterial activity against gram-positive and gram-negative bacteria including PS Aeruginosa, Keleb peneumonia, Staph coccus aureus, Staph sapropphyticus, and Esherichia coli.