Flavonoids are a heterogeneous aggregate of polyphenolics commonly present in fruit and vegetables and other medicinal plants. Because of their simultaneous characteristics as strong antioxidants and efficient anti-inflammatory agents, the compounds have sparked significant scientific interest as both cancer preventatives and very good adjunctive treatment of the disease. This utilization mode of action works by the inhibition of oxidative stress and reduction of persistent swelling, which are two key causal components of carcinogenesis. Antioxidant effects of the flavonoid are based mostly on the ability to destroy reactive oxygen species (ROS), delay lipid peroxidation, or increase the action of significant natural antioxidant enzymes, such as superoxide dismutase and catalase. Inhibition of the pro-inflammatory cytokines (e.g., tumor necrosis factor-6), cyclooxygenase-2 (COX-2), and inhibition of transcription factors (e.g., nuclear factor-6B) are also other anti-inflammatory actions. All of the mentioned effects interfere with the presence of an inflammatory microenvironment that contributes to the occurrence and development of tumors. The flavonoids also disrupt the drug resistance mechanism and susceptibility of the cancer cells to the chemotherapy determinants and reduce the phenomenon of multidrug resistance by increasing the efficiency of efflux transporters such as P-glycoprotein. Clinical usefulness of flavonoids is an expanding area, with the previous finding that flavonoids provide synergistic effects when combined with standard chemotherapy and radiotherapy. This is encouraging, but they need to carry out large-scale placebo-controlled clinical trials to establish its effectiveness, besides establishing the best dosage regimens. Limited clinical evidence indicates that flavonoids may prove beneficial when used as a co-therapeutic agent with conventional chemotherapy. Nanoparticle delivery models, as well as structural manipulation, are some of the strategies that are being developed to improve pharmacokinetic delivery. In general, the chapter outlines the versatile impact of flavonoids in the treatment of cancers and cancer prevention as antioxidants and anti-inflammatory agents and suggests progress in terms of using the described compound and its variants in treating and preventing cancer.