Numerous studies have focused on techniques that are able to break the cell walls to facilitate the diffusion of intracellular bioactive compounds of interest. Among the technologies used, ultrasound-assisted extraction (UAE) has received considerable attention due to its positive influence on heat and mass transfer and since it is considered a green technology. This chapter presents the status and applications of ultrasound-assisted extraction of biologically active compounds from microalgae. The other important physical factors governing the ultrasound-assisted extraction are frequency and sonication time. The choice of solvent depends on the targeted bioactive compounds and also on the solvent properties such as viscosity, surface tension and vapour pressure. In some cases, lower frequencies are required in the processes to avoid degradation of bioactive compounds. Despite the possibilities that the UAE technique offers, few have investigated ultrasound extraction of bioactive compounds from marine species and aquaculture products, especially the extraction/isolation from these species.