Cancer is a significant health challenge worldwide, and oxidative stress plays a key role in its development and progression. Excessive oxidative stress can damage healthy cells, leading to mutations and uncontrolled cell growth. Traditional cancer treatments like chemotherapy and radiation can also increase oxidative stress, causing harmful side effects. To overcome these issues, researchers are exploring green nanomedicine, which uses plant-based biogenic nanoparticles as a natural and effective approach to cancer treatment. Biogenic nanoparticles are tiny particles synthesized using plant extracts. These nanoparticles are environmentally friendly, cost-effective, and rich in bioactive compounds with antioxidant and anticancer properties, enhancing the effectiveness of cancer therapies. Additionally, plant-based nanoparticles can be designed to target cancer cells, minimizing damage to healthy tissues specifically. Recent studies have shown that nanoparticles synthesized from medicinal plants like turmeric, green tea, and neem can inhibit cancer cell growth, induce cell death, and improve drug delivery. These nanoparticles can also enhance the body’s natural defense mechanisms against oxidative stress. The use of biogenic nanoparticles in cancer treatment represents a promising, less toxic alternative to conventional therapies. This chapter will discuss the role of oxidative stress in cancer, the advantages of plant-based nanoparticles, and their potential in green nanomedicine. By integrating nanotechnology with natural plant compounds, we can develop safer and more efficient cancer treatments for the future.