In this study, Fe3O4/ZnO/chitosan magnetic nanoparticles were synthesized by an ultrasound-assisted coprecipitation method. The magnetic nanoparticles were characterized by XRD, FT-IR, FESEM, and VSM techniques. The effects of ultrasonication time and content of chitosan on crystal size and lattice parameters of the nanoparticles were also studied via XRD spectra. FESEM measurements revealed that the coating consists of Fe3O4/ZnO nanoparticles of 15-20 nm in diameter homogeneously dispersed on the surface of chitosan substance. The VSM measurements at room temperature showed that the Fe3O4/ZnO/chitosan nanoparticles had superparamagnetic properties. These results indicated that ultrasonication time and chitosan content had a significant effect on the characteristics of nanoparticles. The antibacterial activities of the Fe3O4/ZnO/chitosan were tested against both gram-positive Saccharomyces cerevisiae and Bacillus subtilis and gram-negative E. coli bacteria using a disk diffusion method.