Biological methods for the synthesis of nanomaterials have been suggested as an ecofriendly alternative for chemical and physical methods. The synthesis of Nickel oxide nanoparticles (NiO NPs) is reported in this paper using Solanum trilobatum leaf extract as the fuel and nickel nitrate as the precursor through hot plate combustion method. X-ray diffraction (XRD) studies exhibited a face centered cubic phase with high crytallinity and an average crystallite size of 23.21 nm. A cylindrical and rod like surface morphology was confirmed from morphological studies, and the average particle size calculated from High resolution transmission electron microscopy (HR-TEM) matches well with XRD results. The NiO formation with high purity phase was confirmed by Fourier transform infrared (FT-IR) spectra. Diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectroscopy were used to study the optical properties, where a band gap of 3.59 eV and intense emission peaks near UV and visible region was observed. Magnetization studies of the synthesized nanomaterial exhibited ferromagnetic nature. The as-synthesized NiO nanomaterial was investigated towards A549 cell culture for cytotoxic activity, antibacterial activity against various gram positive and gram negative bacterial pathogens and Photocatalytic degradation (PCD) of 4-Chlorophenol (4-CP), an effective endocrine disrupting chemical. The synthesized NiO nanoparticles exhibited superior performance towards A549 cells and effective antibacterial activity against gram positive pathogens than gram negative pathogens. It also proved to be a photo catalytically active material through effective degradation of 4-Chlorophenol under UV light, which is well evident from TOC experimental results. © 2020