Metallic nanoparticles synthesized via plant extracts under green chemistry principles exhibit unique physicochemical and biological properties. In this study, for the first time, gold nanoparticles (AuNPs) and copper oxide nanoparticles (CuO NPs) were synthesized using Ziziphus jujuba Mill. fruit extract as a natural reducing and stabilizing agent. The biosynthesized nanoparticles were comprehensively characterized by UV-Vis, SEM-EDX, TEM, FTIR, XRD, and DLS analyses, confirming their nanoscale size, crystalline structure, and surface functionalization by plant-derived biomolecules. The antioxidant potential of the nanoparticles was evaluated using DPPH and ABTS radical scavenging assays, revealing effective free radical scavenging activity, with AuNPs exhibiting comparatively higher antioxidant performance. Cytotoxicity studies performed on A549, MDA-MB-231, and SH-SY5Y cancer cell lines demonstrated a significant, concentration-dependent reduction in cell viability, while relatively lower toxicity was observed in healthy L929 fibroblast cells. Notably, CuO NPs showed stronger cytotoxic effects compared to AuNPs, highlighting differences in their biological behavior. This study emphasizes the novelty of jujube fruit extract-mediated synthesis of both AuNPs and CuO NPs and demonstrates their promising antioxidant and anticancer potential, underscoring the role of plant-derived phytochemicals in the development of sustainable nanomaterials for biomedical applications.