In this research, zinc oxide (ZnO) nanoparticles doped with different percentages of produced cobalt using the green synthesis method. ZnO nanoparticles showed good cellular and microbial toxicity due to their high surface-to-volume ratio. Adding cobalt metal to the nanostructure can lead to the appearance of a new feature. To investigate the effect of adding cobalt metal, synthesized ZnO nanoparticles containing 3 and 6% cobalt were synthesized using plant extract. The resulting nanostructures were characterized by a Raman spectroscopy, UV-Visible spectrometer, X-ray diffraction, and Field emission scanning electron microscopy. Ultimately, the synthesized samples' cytotoxicity and antimicrobial tests were performed. XRD confirmed the formation of a hexagonal wurtzite ZnO structure. XRD and electron imaging showed that doping resulted in a decrease in average crystal size. The results showed that with cobalt doping, the particle size decreased slightly. The cytotoxicity and antimicrobial effects results showed that in all three studies, cobalt doping leads to an increase in the toxicity of this nanostructure compared to non-doped nanoparticles.