Oil migration is a common problem in chocolate confectionery products leading to quality defects, particularly fat bloom. Several factors such as contact area, ratio of the two fat phases, type of the fat, solid fat content, presence of non-fat solid particles, particle size, viscosity, structure, concentration gradient of triacylglycerols (TAGs), and storage temperature have all effect on migration rate. Mechanism of oil migration has still not been clearly understood, but possible mechanisms have been suggested and studied in the literature. Diffusion mechanism was demonstrated and modeled in many studies. Although there are so many methods to monitor and quantify migration, magnetic resonance imaging (MRI) is among the most promising techniques as being non-destructive. This review covers the literature related to basics of migration, mechanisms, and monitoring and modeling migration in chocolate through MRI and also includes a brief description about chocolate, chocolate processing, and fundamental concepts in MRI.