In this study, we focus on the synthesis of citric acid (AC) coated silver-cobalt ferrite nanoparticles (AC coated CFO.Agx NPs, note as CAx NPs) by hydrothermal method combined mechanochemical ligand exchange process. The structure, morphology and magnetic properties of CAx NPs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). The solubility and stability of some CAx NPs solution have been investigated, aqueous solution of 1 mg/mL CA0.2 are stable in neutral medium for up to one month. CAx NPs were evaluated the antibacterial ability by disc diffusion test (Kirby-Bauer method) against Gram-negative Pseudomonas aeruginosa (PA) and Gram-positive Staphylococcus aureus (SA) bacterial in vitro. At the same concentration of 0.25 mg/mL, the antibacterial activity of samples depended on the ratio of Ag doping: The zone of inhibition diameter for SA and PA increased as the Ag content gradually increased from x = 0.05 to 0.2 and decreased slightly as further increasedpass to 0.2. The largest zone of inhibition diameter for SA and PA of CA0.2 NPs are 32 and 36 mm, respectively. The hyperthermia studies showed that the CA0.2 NPs was highly suitable for magnetic hyperthermia applications