BACKGROUND: The metal oxide nanoparticles possess unique properties such as biological compatibility, superior reactivity, and capacity to develop reactive oxygen species, due to this they have drawn significant interest in cancer treatment. The various MONPs such as Cerium oxide, Copper oxide, Iron oxide, Titanium dioxide, and Zinc oxide have been investigated for several types of cancers including brain, breast, cervical, colon, leukemia, liver, lung, melanoma, ovarian, and prostate cancers. However, traditional physiochemical synthetic methods for MONPs commonly include toxic materials, a major concern that raises questions regarding their biocompatibility and safety. OBJECTIVE: This study aims to investigate the role of plant phytoconstituents in the development of MONPs via green synthesis and explore the therapeutic effectiveness of MONPs in treating several types of cancer. Primarily, it examines the potential of plant phytoconstituents (phenolic compounds, flavonoids, glycosides, alkaloids, etc.) in the development of MONPs as well as their improved ability to target numerous types of cancer. METHODS: A systemic search was conducted on recent literature, focusing on developing green MONPs by utilizing plants' phytoconstituents (plant extracts). The study of plant phytochemicals (present in different parts of a plant such as leaves, flowers, stems, peels, and roots) and their role in the synthesis of green metal oxide nanoparticles as well as their anticancer activity against several types of cancers was analyzed. Also focusing on their anticancer mechanism that involves ROS production, generates oxidative stress, and apoptosis leads to cancer inhibition. RESULTS: Phytochemicals-mediated metal oxide nanoparticle synthesis revealed many advantages such as improved biological compatibility and enhanced sensitivity towards cancer cells. Phytochemicals present in plant extracts act as natural capping, reducing, and stabilizing agents, enhancing nanoparticle synthesis which leads to synergistic anticancer activity. Additionally, the natural antioxidant and anticancer activity of various phytochemicals enhances the therapeutic potential of metal oxide nanoparticles, producing them more effective against ROS-generated apoptosis and showing negligible toxicity towards normal cells. CONCLUSION: The utilization of plant phytochemicals in metal oxide nanoparticle production presents a safe, eco-friendly, sustainable, and effective approach to developing effective and safer cancer nanomedicines. Green synthesis not only increases anticancer activity but also decreases the biocompatibility problems associated with the physiochemical synthetic approach. Further research needs to concentrate on improving this synergy to create a targeted phytochemical-based metal oxide nanoparticle for cancer therapeutics.