In this study, Macroptilium lathyroides leaf extract was used as a reducing and capping agent to prepare the biogenic CuO-NiO nanocomposite. The synthesized samples were analyzed using UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), High-resolution transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy with energy-dispersive X-ray (EDX) analysis, Dynamic light scattering, and Zeta potential. The structure, surface morphology, elemental compositions, and stability of the particles were determined. The average size of the particles from TEM was found to be 10.6 nm with a cubic structure. Furthermore, CuO-NiO nanocomposite was used to study the methylene blue dye degradation when exposed to sunlight for 90 min, about 98.1 % of the dye degraded. The nanocomposite showed high antimicrobial activity against both Gram-positive bacteria Staphylococcus aureus (18 mm), Streptococcus pyogenes (20 mm) and Gram-negative strains Klebsiella pneumonia (16 mm), Escherichia coli (18 mm) at 30 µg/mL. The antifungal activity against Trichoderma viride (14 mm), Candida albicans (13 mm) and excellent antioxidant properties with an IC50 value of 184.52 µg/mL were observed. Furthermore, it shows potent cytotoxic effects against the lung cancer cell line A549, and breast cancer cell line MCF 7 with an IC50 value of 59.8 µg/mL, 42.90 µg/mL, respectively.