In this work, a novel bactericidal agent based on two-dimensional Pd@Ag nanosheets (Pd@Ag NSs) that is responsive to near-infrared (NIR) light has been developed. These Pd@Ag NSs were prepared by reducing silver ions on the surface of Pd nanosheets (Pd NSs) seeds by formaldehyde, and displayed excellent NIR absorption and photothermal conversion properties. In addition, the NIR irradiation triggers the release of more Ag from the Pd@Ag NSs. Upon exposure to a NIR laser at a low power density (0.5 W cm), Pd@Ag NSs kill both Gram-negative (Escherichia coli, E. coli) and Gram-positive (Staphylococcus aureus, S. aureus) bacteria effectively by the synergistic effect of plasmonic heating and Ag release, which is much higher than either plasmonic heating or Ag alone. Such a novel nanomaterial is promising as an adjuvant therapeutic method for the treatment of patients suffering from severe bacterial infections.