There is a strong economic and ecologic demand for crystallization platforms which are significantly more efficient, flexible, and allow an improved control over the crystallization process. In this way higher quality crystals can be achieved which are required for application in personalized medicine and controlled drug release systems. Ultrasound crystallization is a promising tool to achieve these high quality crystals because it improves the reproducibility of the crystallization process and allows to control the particle size and shape. The goal of this doctoral project was to investigate how ultrasound can be applied in an efficient way during crystallization processes. The advantages of ultrasound like faster nucleation, the formation of smaller particles and impact on particle shape were already presented in literature. A thorough investigation about the optimal ultrasound settings, particularly the frequency and cavitation bubble type, to enhance crystallization was, however, lacking. Mostly, off the shelf equipment was used, designed for other applications like cleaning or dispersion. In addition, most mechanisms behind the ultrasound effects are unknown. This doctoral research defines the optimal ultrasonic frequency and cavitation bubble type to enhance the nucleation rate, the degradation rate, the micromixing efficiency and the fragmentation rate of paracetamol crystals. Furthermore, the sonoprecipitation of manganese carbonate was investigated. The findings of this doctoral research contribute to the development of efficient crystallization processes according to the principles of Process Intensification.