Ultrasound-assisted extraction (UAE) is one of the most widely researched alternative technologies to obtain food additives and nutraceuticals from biosources. The working principle of UAE is the generation of acoustic cavitation in the extraction medium, which enhances the extraction efficiency by the combined effects of fragmentation, erosion, and destruction of raw materials as well as by improving the penetration of solvent inside cells and mass transfer of intracellular compounds. The degree of cavitation depends on several factors, such as the frequency and intensity of ultrasound and matrix characteristics. The present chapter focusses on the current knowledge of UAE and its application to extract various added-value compounds from plants, algae, and food processing by-products. It provides an overview of the principles, operation, and advantages and disadvantages of the technique. Emphasis has been placed on demonstrating the efficiency of UAE to obtain major food additives, including polyphenols, colorants, lipids, stabilizers, and proteins.