NiO-ZnO mixed metal oxide nanocomposite was synthesized via chemical homogeneous precipitation method. The synthesized nanocomposite was also characterized by XRD, FESEM with EDS, FTIR, and UV. XRD exhibit an average crystallite size of 29 nm. The elemental composition obtained from EDS shows a nearly equal concentration of Ni and Zn with an atomic ratio of Ni/Zn = 0.96. The particles of nanocomposite are highly stable throughout a wide range of pH. The DLS exhibit an average hydrodynamic particle size similar to 49 nm. The high pore diameter and pore volume of nanocomposite obtained from BET exhibited a high photocatalytic activity for the removal of methylene blue (MB) dye under UV light irradiation. The kinetics of photocatalytic reduction of MB followed the Langmuir isotherm model, suggesting homogeneous surface adsorption of MB on the surface of the nanocomposite. NiO-ZnO nanocomposite was also found to be an effective antibacterial agent against Gram positive bacteria (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli). Colony forming unit plate counting method showed that 95% and 85% of S. aureus and E. coli respectively were killed by the nanocomposite. Also, this suggested that nanocomposite was more effective towards S. aureus than E. coli. Release of intracellular components was evident from FESEM image of nanocomposite-bacteria cell, cell integrity study, and cell permeability study. This included the release of electrolytes, nucleic acid, and proteins, ultimately leading to cell lysis. (c) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.