The use of plants and microorganisms as biological synthesizers of nanoparticles is considered the future of modern agriculture, as chemical nanosynthesis and excessive use of fertilizers and pesticides to improve plant growth and control plant diseases and insects have had very negative effects on the environment. This chapter investigates the forms of copper nanoparticles (CuNPs) that have been used recently in plant protection, listed the growing importance of these particles in this area. It has been clarified that copper oxide nanoparticles are considered one of the most widely used forms in the field of agriculture, followed in importance by copper sulphate. The availability of many plants that can be used in the biosynthesis of copper nanoparticles makes the green synthesis of nanoparticles cheaper and easier than other biological methods. This chapter demonstrated how easy it is to synthesize nanoparticles using plant extracts. Other biological methods for synthesizing copper nanoparticles using microorganisms such as bacteria, fungi, viruses and algae were discussed. Characterization methods such as UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscope (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), atomic absorption spectroscopy (AAS), energy dispersive spectroscopy (EDS), surface enhanced residual spectroscopy (SERS), beam photoelectron spectroscopy (XPS), X-ray diffraction (XRD), high-angle annular dark field (HAADF), dynamic light scattering (DLS) and zeta potential are demonstrated in detail. Finally, the application of copper nanoparticles in plant protection as a pesticide, bactericide, and fungicide was demonstrated and showed that the use of biologically synthesized copper nanoparticles was very effective against plant pests and pathogens.