In this paper, hybrid nanocomposites of modified carbon nanotubes (MWNT-COOHs) (FCNTs) with silver nanoparticles and atenolol were prepared by wet chemical process and investigated by X-ray diffraction, scanning electron microscopy (SEM). About 29 nm of silver particle is determined in SEM micrographs. Silver nanoparticles were virtually fixed on the surface of the functionalized nanotubes. Nanocomposites have excellent antibacterial activities against Escherichia coli (E. coli), so in vitro antibacterial tests were performed to determine the antibacterial capability of the Ag/FCNTs nanocomposites.