We attempted to synthesize nickel oxide nanoparticles (NiO-NPs) utilizing waste Arachis hypogaea (peanut) shell extract and studied their structural, morphological, and biological performance for biomedical applications. The green engineered NiO-NPs possessed a face-centered cubic structure with an average particle size of 20 nm in highly crystalline form. NiO-NPs were shown to have an optical resonance peak at 327 nm with 3 eV as the optical band gap according to the UV–visible spectra, and the stretching band between Ni–O were evidenced from the FTIR and Raman spectrum. Utilizing green approach the stable nanoparticles were obtained with average particle size of 31 nm from SEM analysis; zeta potential value of −17.6 mV, and PDI as 0.68, revealed the formation of spherical nanoparticles with distinct morphologies without aggregation. XPS analysis confirmed the oxidation states of the elements Ni (2p) and O (1s). This approach may help to increase the surface area, increasing the possibility of nanoparticles interacting with bacterial cells. Furthermore, the presence of nickel and the oxygen oxidation state were confirmed by XPS. Proteus vulgaris, Streptococcus oralis, Bacillus subtilis, and Escherichia coli were found to be susceptible to the antibacterial action of the produced NiO-NPs, with a maximal zone of inhibition of 10.25 mm at 500 μg/ml for P. vulgaris. For P. vulgaris and E. coli, the minimum inhibitory concentrations of NiO were 5.36 and 12.55 %, respectively, at 31.25 μg mL⁻¹. We hereby claim that green engineered NiO NPs decorated with A. hypogaea shell extract have great potential for pharmaceutical and biomedical applications.