Crystallization has been applied to a broad range of industries such as bulk and fine chemicals and the pharmaceutical and food industries. It is important to strategically control the in situ purification process during crystallization to meet the regulatory and functional specifications of the crystals. While the control of the crystallization–purification process has been widely discussed for batch crystallizers, there has been little focus with the literature on controlling purification for continuous crystallizers. Continuous crystallization is a more intensified approach to crystallization, with lower capital footprint and potentially offering more consistent quality control. This review paper provides an in-depth discussion of the strategies and scientific understanding in controlling the crystallization–purification process in continuous crystallization. In particular, it describes how scientific understanding in the purification process, generated so far for batch crystallization, can be translated to continuous crystallization.