Flavonoids may be natural components came from many vegetables and fruits. A variety of heath effects of these compounds were found. However, a few safety studies indicated that certain adverse effects of these compounds could influence on human health, which could involve genotoxic/carcinogenic effects or interaction with thyroid hormone biosynthesis. Isoflavones' estrogenic activity could influence on sexual development of young animals and children. Furthermore, flavonoids could inhibit the absorption of some nutrients, interact with certain drug pharmacokinetics and affect neurobehavioral development. In this paper, the potential toxicities of flavonoids from recently published papers were reviewed.