Sea buckthorn is a rich source of bioactive compounds including carotenoids, polyphenols, polysaccharides, terpenes, organic acids, and phytosterols. These compounds contribute to its various health benefits, such as antioxidant, anticancer, anti-hyperlipidemic, anti-obesity, anti-inflammatory, antimicrobial, antiviral, dermatological, neuroprotective, and hepatoprotective properties. The bioactive composition of sea buckthorn is influenced by several factors including genetic variation, plant part analyzed, climatic and growth conditions, year and degree of harvest, storage conditions, harvest time, and processing and analytic methods. This chapter focuses on key substances such as polyphenols, carotenoids, polypeptides, polysaccharides, terpenes, essential oil, organic acids, phytosterols, phenylpropanoids, and alkaloids.