NiO-based binary and ternary nanocomposites were prepared using a hydrothermal method. The properties of the samples were explored comprehensively using various characterization techniques. The XRD, TEM, HRTEM and XPS results confirmed the composites formation. The synthesized samples were exploited for visible-lightdriven photocatalytic degradation of MB dye. The NiO/ZnO/g-C3N4 shows superior photocatalytic activity than pristine NiO and other binary compounds. The bactericidal activity was analyzed against various bacteria. From the results, it is exposed that the bactericidal activity of NiO was enhanced by the addition of ZnO and, gC3N4. The NiO/ZnO/g-C3N4 nanocomposites showed enhanced antibacterial properties with ZOI of 27 mm against S. aureus and with ZOI of 25 mm and 24 mm against E. faecalis and E. coli., respectively. Based on the existing results, NiO/ZnO/g-C3N4 nanocomposites could be used for the dye degradation process and antibacterial activity against pathogenic bacteria.