Nanotechnology is an emerging field dedicated to manipulating atoms and molecules and demonstrates significant potential across various scientific domains. This innovative discipline focuses on nanoparticles (NPs) with diameters ranging from 1 to 100 nm, capitalizing on their small size and extensive surface area to enhance reactivity. Out of which, copper-based nanomaterial is one of the most used in nanotechnology. Copper and copper-conjugated nanoparticles, synthesized through green approaches, offer economic and eco-conscious advantages. These copper nanoparticles find diverse applications in biomedicine, pharmaceuticals, bioremediation, molecular biology, bioengineering, genetic engineering, dye degradation, catalysis, cosmetics, and textiles. This chapter overviews on the effects and applications of copper nanoparticles, primarily emphasizing green synthesis of copper nanoparticles following their application in seed germination and plant growth.