As a common medicinal and edible plant, dandelion plays a crucial and significant role in the fields of traditional Chinese medicines, functional foods, healthcare products, daily chemicals, and feed additives, which are closely related to its rich chemical constituents and remarkable biological activities. Modern studies have demonstrated that dandelion contains all kinds of bioactive constituents, including flavonoids, amino acids, fatty acids, organic acids, phenolic acids, coumarins, lignans, polysaccharides, phytosterols, terpenes, glycoproteins, oligosaccharides, alkaloids, etc. Meanwhile, dandelion has been proven to possess antioxidant, antibacterial, anti-inflammatory, antitumor, antivirus, hypoglycemic, and hypolipidemic properties, as well as the ability to regulate hormone levels and protect some visceral organs. Among them, flavonoids derived from dandelion and their antioxidant activities have received considerable attention. This study reviews dandelion flavonoids and their in vitro and in vivo antioxidant activities by consulting and organizing relevant domestic and international works of literature to provide a scientific and theoretical basis for further research, development, and utilization of dandelion.