A three-component composite consisted of graphene oxide, cobalt ferrite, and silver nanoparticles has been prepared by a facile method and fully characterized. The antibacterial activity of this composite has been greatly enhanced after being combined with ciprofloxacin drug. This clearly showed the occurrence of a strong synergistic effect between ciprofloxacin and the Ag NPs in the composite. The ciprofloxacin-conjugated composite was found to be a potent antimicrobial agent while having rather low cytotoxicity and high stability. The studies based on field emission scanning electron microscopy (FESEM) analysis and zeta potential measurement have revealed that the composite sticks to the bacterial cell wall causing irreversible cell damage. This multifunctional magnetic nanocomposite was also examined as drug delivery system for ciprofloxacin in solutions with different pH. It was observed that the release of ciprofloxacin in this system is pH-sensitive with gradual and controlled manner. Mechanisms for the synergistic effect and drug release behavior, as well as explanation for the antibacterial action, of the nanocomposite were also demonstrated.