Herein, an extensive study to understand the antibacterial, antioxidant, and antidiabetic activities of Citrus limonium fruit juice-mediated ZnO/MgO nanocomposite synthesis is reported. Its performances are compared with their pristine ZnO and MgO nanoparticle counterparts. The X-ray diffraction (XRD) analysis of the ZnO/MgO nanocomposite reveals the existence of two phases in a single matrix with no other phases. Fourier Transform Infrared (FTIR) spectroscopic analysis of the ZnO/MgO nanocomposite displays the characteristic stretching vibration of Zn-O, Mg-O, and Zn-O-Mg bonds. The bandgap value of the ZnO/MgO nanocomposite is about 3.43 eV, which lies in between the bandgap energies of the ZnO (3.26 eV) and MgO (5.35 eV) nanoparticles. The X-ray photoelectron spectroscopic (XPS) investigations confirm the existence and the chemical state of zinc, magnesium, and oxygen in the ZnO/MgO nanocomposite. Scanning electron microscopic images of the ZnO/MgO nanocomposite display a morphology of porous, uneven grains. The ZnO/MgO nanocomposite reveals better antibacterial activity with a zone of inhibition value of 26.6 mm against Staphylococcus epidermidis and 25.4 mm for Escherichia coli at 150 µg/mL concentration, respectively. Similarly, the nanocomposite exhibits a better DPPH free radical scavenging capacity, with 92.2 % inhibition at 850 µg/mL concentration. Further, the ZnO/MgO nanocomposite shows a maximum enzyme inhibitory activity of 82.1 % and 82.9 % against the α-amylase and α-glucosidase enzymes at 850 µg/mL concentration, respectively. Thus, the green-derived ZnO/MgO nanocomposite exhibits intriguing biological features, emphasizing that it continues to be explored as a potential biomedical material.