A new three-component and magnetically responsive NiFe 2 O 4 @PANI@Ag nanocomposite has been fabricated by coating of nickel ferrite, NiFe 2 O 4 , nanoparticles with polyaniline (PANI) and subsequent immobilization of silver nanoparticles onto the surface of polyaniline shell. The as-prepared nanocomposite has been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM). The saturation magnetization of the NiFe 2 O 4 core decreases dramatically after coating with polyaniline and silver nanoparticles, however, the nanocomposite NiFe 2 O 4 @PANI@Ag can be still separated from solution media through magnetic decantation. The antibacterial activity of the synthesized nanocomposite was studied and compared with those of naked NiFe 2 O 4 , NiFe 2 O 4 @PANI and some standard antibacterial drugs.