Sea buckthorn is a valuable plant resource, rich in flavonoids and phenolics, which possess various physiological activities and medicinal values. This chapter primarily discusses the chemical composition and pharmacological effects of these flavonoids and phenolics found in sea buckthorn. Flavonoid compounds encompass flavones, flavonols, isoflavones, anthocyanins, and their derivatives. The phenolic compounds in sea buckthorn fruits predominantly include flavonoids, phenolic acids, proanthocyanidins, and other phenolic compounds. These compounds play significant roles in antioxidant activity, combating obesity and diabetes, antitumor activity, and osteoporosis. Given these characteristics, there are broad prospects for the application of flavonoids and phenolics in fields such as food, medicine, and other health care products.