The study aimed to synthesize copper nanoparticles (CuNPs) using Brassica oleracea var. gemmifera extract (BOE) and investigate their antioxidant and antibacterial properties. The BOE- mediated CuNPs (BOE-CuNPs) were successfully synthesized utilizing reducing and stabilizing properties of B. oleracea var. gemmifera extract. The nanotechnology features showed that BOE-CuNPs were nano in size (106.59 ± 4.77 nm), slightly agglomerated, stable (-12.41 ± 1.88 mV), and made up of mainly copper. The green synthesized BOE-CuNPs have potential antioxidant features and have EC50 values (concentration essential to inhibit 50% of free radicals) of 334.09 ± 17.70 μg/mL and 361.43 ± 12.91 μg/mL in DPPH and ABTS free radical scavenging activity, correspondingly, and could be useful in treating oxidative-stress-mediated conditions. Also, as-synthesized BOE-CuNPs have potential antibacterial activity and showed the highest antibacterial activity against Escherichia coli – MTCC 41 and Listeria monocytogenes – MTCC 657, and could be useful as an antibacterial representative in the biomedical field. However, to utilize BOE-CuNPs, an in- detailed functional and toxicological profile of BOE- CuNPs needs to be performed. Keywords:- Copper Nanoparticles, Brassica oleracea var. gemmifera, Green Synthesis, Antioxidant Activity, Antibacterial Activity.