Cancer continues to be a leading cause of mortality worldwide, with rising prevalence linked to genetic abnormalities, epigenetic alterations, detrimental lifestyle choices, and an aging demographic. Conventional cancer treatments, such as chemotherapy, radiation, and immunotherapy, while somewhat successful, sometimes entail significant adverse effects, drug resistance, and restricted access to tumor tissues, especially in advanced-stage tumors. These problems have exacerbated the quest for alternative and complementary therapy. Flavonoids, a category of naturally occurring polyphenolic chemicals present in several fruits, vegetables, and medicinal plants, have garnered significant interest for their anticancer properties. Compounds such as kaempferol, quercetin, apigenin, and diosmin demonstrate several modes of action, including antioxidant properties, reduction of tumor cell growth, activation of apoptosis, and suppression of angiogenesis and metastasis. Moreover, flavonoids have demonstrated the capacity to regulate critical signaling pathways implicated in cancer advancement, including the PI3K/Akt, mTOR, and JAK/STAT pathways. Recent breakthroughs in nanotechnology have improved the bioavailability and targeted distribution of flavonoids, hence enhancing their medicinal efficiency. This chapter underscores the potential of flavonoids in cancer prevention and treatment, examines the incorporation of flavonoid-based nanoparticles in augmenting cancer therapy, and stresses the necessity for additional research to assess their safety, pharmacokinetics, and synergistic interactions with standard therapies.