Flavonoids are phenolic compounds that are generally found in foods and beverages of plant source. Based on their chemical structures, flavonoids are classified into six major subclasses as flavones, flavonols, flavanones, flavanols, anthocyanins, and isoflavones. Their inherent antioxidative, anticarcinogenic, antiallergenic, antiinflammatory, antibacterial, antidiabetes, antimutagenic, and antitumor activities are considered as beneficial for human health. However, the use of flavonoids as nutraceutical, pharmaceutical, medicinal, and cosmetic agents is limited due to their weak solubility in water accompanied with poor stability, apparently limiting the bioavailability. The sugar moiety has important role in determining the absorption and bioavailability of flavonoids. Glycosylation of flavonoids is considered an effective method to rise their solubility and stability in water. This chapter describes the enzymatic method for the synthesis of flavonoid glucosides and characterization of their biological properties.