The development of new antibacterial agents that are highly effective are of great interest. Herein, we present a recyclable and synergistic nanocomposite by growing both iron oxide nanoparticles (IONPs) and silver nanoparticles (AgNPs) on the surface of graphene oxide (GO), obtaining GO-IONP-Ag nanocomposite as a novel multifunctional antibacterial material. Compared with AgNPs, which have been widely used as antibacterial agents, our GO-IONP-Ag shows much higher antibacterial efficiency toward both Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus). Taking the advantage of its strong near-infrared (NIR) absorbance, photothermal treatment is also conducted with GO-IONP-Ag, achieving a remarkable synergistic antibacterial effect to inhibit S. aureus at a rather low concentration of this agent. Moreover, with magnetic IONPs existing in the composite, we can easily recycle GO-IONP-Ag by magnetic separation, allowing its repeated use. Given the above advantages as well as its easy preparation and cheap cost, GO-IONP-Ag developed in this work may find potential applications as a useful antibacterial agent in the areas of healthcare and environmental engineering.