<p>Nanomaterials have emerged as a key area of research because they exhibit unique properties and potential applications in several fields such as catalysis, energy storage, biomedical and environmental remediation, etc. Recently, there has been significant interest in nanomaterials due to their superior antibacterial activity against multidrug-resistant bacteria compared to conventional antibiotics. In this context, the present study aims to synthesize composite nanomaterials of CuO and NiO using the co-precipitation technique and investigate their structure, microstructure, antibacterial, and antioxidant efficacy, thereby exploring their potential practical applications. Structural studies carried out using X-ray diffraction and Raman spectroscopy show the cubic structure of NiO, the monoclinic structure of CuO, and the mixed structure of CuO/NiO composite nanomaterials. A microstructural study reveals the spherical shape of the nanomaterials, with the particle size in the range of 50–70&#xa0;nm. The agar well diffusion method was utilized to investigate the antibacterial activity of nanomaterials against three Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, and Corynebacterium rubrum) and three Gram-negative bacteria (Salmonella typhimurium, Escherichia coli, and Pseudomonas aeruginosa). Composite nanoparticles exhibit better antibacterial activity against microorganisms than the traditional antibiotic, tetracycline. However, NC25 nanoparticles show greater antibacterial effects against S. aureus and S. typhimurium among all the tested nanomaterials. All the composite nanomaterials exhibit greater antioxidant activity when compared to the NiO and CuO nanoparticles. NC25 and NC50 exhibit the maximum scavenging activity for ABTS and DPPH, respectively. Our findings indicate that CuO/NiO composite nanoparticles could be very useful for environmental and medical applications like antimicrobial coatings, materials for healing wounds, and antioxidant additives.</p>